Dr. Kevin Collins arrived in Port Charles on December 3, 1993. He came to town to study his identical twin brother, serial killer Ryan Chamberlain, who had been imprisoned in Pentonville. Kevin hadn't seen his brother in 30 years, since their father had left his wife, taken Kevin, and moved overseas. Kevin had read about his twin's case in several psychiatric journals, and he had wanted to learn more about the serial killer that he shared DNA with. Kevin's reception in Port Charles was cold, as he was initially mistaken for his diabolical brother. Ryan was equally hostile and initially denied that he had a brother, despite being confronted with his identical twin.

Eventually, Kevin proved himself to be a decent man, and he became close friends with Mac Scorpio and Felicia Jones. Ryan had been obsessed with Felicia since he had met the young divorced mother in Texas. Kevin visited his brother, Ryan, several times as he settled into Port Charles, and Kevin thought that Ryan had been making progress. However, he was unaware that Ryan had been manipulating Kevin in an effort to escape the mental hospital and stop Felicia's wedding to Mac.

In August 1994, during one of Kevin's visits, Ryan knocked Kevin out then impersonated him in Port Charles. Kevin eventually managed to prove to the authorities and hospital personnel that he was indeed Kevin Collins and not his evil twin. Kevin raced to the church to stop Ryan from ruining Felicia's wedding. After Ryan was apprehended, Kevin paid his brother a visit, and he wiped his hands of Ryan. However, Ryan wasn't through with Kevin. He managed to escape the prison and impersonate Kevin briefly in order to kidnap Felicia's baby. Kevin helped Mac and Felicia find Ryan and the baby in Canada.

On March 24, 1995, Ryan was presumed killed in an explosion. Georgie had been found safe and reunited with her mother. Kevin tried to pick up the pieces. He had some help from Lucy Coe, whom he had become involved with prior to Ryan's escape. However, Kevin began to have strange and disturbing dreams. Kevin was haunted by the death of his former lover, Grace Reese, who had drowned in a car that he'd been a passenger in. Kevin blamed himself for Grace's death, so Lucy urged him to see a psychiatrist. Under hypnosis, Kevin realized that Grace had been driving the car as it had plunged into the lake and that he had been knocked unconscious in the car.

1996 kicked off with Lucy and Kevin in a strong and loving relationship until Kevin started experiencing hallucinations and blackouts. He also started to act erratically, while teaching a psychology class at Port Charles University. Mac's niece Robin, who had taken one of Kevin's classes, noticed it, and she called him on it when he mistreated a student. Kevin started to lose more time that he couldn't account for, and he began to stalk Felicia Jones like his twin had. Things reached a crisis point when Kevin kidnapped Felicia then took her to his childhood home on Jasmine Island, where he held her captive as he began to remember more of his traumatic childhood.

Lucy managed to talk her way into the house then provide Felicia with an opportunity to escape. Afterwards, Lucy slowly got Kevin to open up about the day when he'd been eight years old and had pretended to be Ryan. His cold and indifferent mother had always acknowledged that Kevin was the good twin, but she had never had much to do with him. Instead, Melanie had always singled out Ryan to spend time with. However, the twins had learned that they could trade places without their parents being any the wiser.

When Melanie had gone looking for Ryan, Kevin had stepped up, pretending to be his brother. Melanie had taken an unsuspecting Kevin into her private bathroom, where she had sexually assaulted him. Traumatized, Kevin had promised his brother that he would tell their father the truth about what Melanie had been doing to Ryan. To Kevin's surprise, Victor Collins had packed up Kevin and had left both his wife and Ryan on Jasmine Island. Kevin had been raised in Europe and told never to speak of his brother or Ryan's secret again.

Lucy stood by Kevin when he was charged with kidnapping and stalking Felicia. Felicia was angry at first, but she dropped the charges when she realized that Kevin hadn't intentionally tried to hurt her. Kevin began treatment with Dr. Gail Baldwin, and his medical license was suspended.

On December 23, 1996, Kevin and Lucy were in a better place. Kevin regretted that he had a hard time expressing his deep love for Lucy, but he tried to trust her with his secrets. Kevin confided that he'd had a vision of him and Ryan as children dancing on their mother's grave and celebrating that she was dead. He feared that a dark side in him was fighting to be free, but Lucy helped him understand that his reaction had been perfectly normal.

In early January 1997, Lucy made an unsettling discovery when she found a box of old letters in Kevin's closet. In session, Kevin confessed to Gail that he feared that he would not live up to people's expectations, but Gail suspected that Kevin feared he wouldn't live up to his father's expectations. Meanwhile, Lucy had turned to Gail for advice because Lucy feared that Kevin was hiding something. Gail urged Lucy to give Kevin some space to work things out for himself, but Lucy couldn't let it go, and she began to dig for information about Victor Collins.

On March 3, Kevin announced that he was headed for a trip to Arizona, but at the airport, he had booked a flight to England. When Kevin returned home on April 9 -- a few days early -- Lucy was upset. Lucy had watched a tape of Serena, the child that she had carried for Scott Baldwin and her best friend Dominique. Lucy admitted that she wanted to have children. Kevin assured her that she would be a great mother, but later that evening, Lucy discovered that Kevin had lied to her about his travel plans to Arizona.

Days later, Kevin surprised Lucy with a painting that he'd made of her and her beloved duck, Sigmund. Touched, Lucy admitted that he vexed her, and they discussed his trip to England. He claimed that he'd gone to England to ask his father's work colleagues to stop sending him letters of his father's mathematical equations. Lucy suspected that Kevin was still hiding something, so she decided to team up with Felicia to find out what it was.

In time, Felicia and Lucy discovered that Kevin had been sending packages to a convent, called the Sisters of Most Holy Sacrifice, located in France. Felicia and Lucy posed as nuns to find out why Kevin had been sending the packages, but Kevin had been a step ahead of them and had warned the nuns to be on the lookout for Felicia and Lucy. Soon, Kevin and Mac followed the ladies to Europe.

On May 21, Kevin confessed that he'd been hiding the truth about his father. Victor Collins hadn't died; he was alive but mentally ill and confined to a bed in the convent. Kevin hadn't seen his father in years, but his father periodically sent him letters with mathematical equations. As Kevin reminisced about his father, he revealed that his father had often referred to him as "Monk," which had been short for monkey because Kevin had been a hyperactive child who had climbed on everything.

Lucy broached the subject of moving Victor to Port Charles, but Kevin admitted that he resented his father for leaving Ryan behind with a mother who had sexually abused her child. However, Kevin made arrangements for Victor to be transferred to General Hospital for treatment. Gail agreed to monitor Victor's case.

In June 1997, Kevin was unable to practice medicine, so he wrote a fictional murder mystery novel called General Homicide. The novel was a bestseller, and the characters were based on people that Kevin had known from working at GH. However, the book caught the attention of a real killer. The serial killer targeted doctors and nurses on staff and recreated murder scenes from the successful book. Kevin turned to his best friend Mac, the police commissioner, for help. Kevin was shot when he got close to solving the crimes. The killer turned out to be Greg Cooper, a doctor who had been kicked out of his internship because the Quartermaines had given the position to Karen Wexler after Greg had been determined to be unstable.

On November 23, 1998, Kevin and Eve found a birth certificate for Greg Cooper that revealed that Greg was the love child of Kevin's father and Victor's mistress, Marcia Cooper. Kevin recalled a traumatic childhood memory of the day that his evil twin, Ryan, had tried to persuade Kevin to play a "knife-throwing" game. Kevin had refused, so Ryan had tossed knives at their father's mistress. Right before she toppled off the edge of the cliff, a horrified Kevin had managed to grab the baby from her arms. That baby had been Greg. Victor denied that he was Greg's father because Marcia had been pregnant when he had met her.

After Greg fell from the same cliff that had claimed his mother's life and was presumed dead, Kevin tried to pick up the pieces. His relationship with Lucy had been rocky. She had miscarried their baby, and their plans for a double wedding with Mac and Felicia fell apart when Kevin learned that Lucy had lied about her role in a car accident that had left Lucy's surrogate daughter, Serena, blind and in need of a cornea transplant. A reconciliation became impossible when Kevin caught Lucy and Scott in bed together following a night of drinking. Kevin turned to colleague and friend Dr. Eve Lambert for support.

By the beginning of 1999, Kevin found himself falling for Eve, and they started dating. Eve was with Kevin on July 12, when he identified his father's body in Rome. Victor had supposedly died of a massive heart attack, but Kevin was skeptical. His father's mind had greatly improved while under Kevin's care, and physically, Victor had been in perfect health. With Eve's help, Kevin broke into the morgue, hoping to get some answers, but they were caught and arrested. Kevin and Eve returned to Port Charles, but Kevin remained haunted by dreams about his father.

In August 1999, Eve and Kevin realized that they shared a strong psychic connection with each other, but neither could recall much of their time in Rome. Determined to ferret out the truth, Eve asked Kevin to put her under hypnosis. Their quest for information led them to Jasmine Island, where they discovered a disheveled Victor, who was very much alive. Victor was weak and his memory scattered because he had stopped taking his medications.

After Victor recovered, he explained that Kevin and Eve had been part of an experiment called the Cobra Project because Kevin had the ability to block ESP. Kevin was more concerned about Eve's visions of a boy because Eve suspected that she'd been lied to about the birth of her stillborn son. On October 12, Kevin realized that his father's mathematical notes over the years had really been a formula to block psychic impulses. Kevin had to keep the formula out of the hands of a man named DV Bordisso, whom Kevin suspected had been behind the Cobra Project.

In November 1999, Kevin and Eve's relationship was tested when DV blackmailed Eve. DV wanted Victor's letters in exchange for uniting Eve with her long-lost son. Eve didn't want to betray Kevin, but she longed for her son. When Kevin learned of Eve's betrayal, he wondered if he would ever be able to trust her again. Consumed by guilt, Eve confessed to what she had done then she agreed to help Kevin, Lucy, and Scott take DV down. However, DV betrayed Eve in the end. He revealed that the image of their son had been a psychic projection to get her to turn on her friends because DV had wanted Eve to feel the pain that he had felt when he had learned that their son had died.

Eve attacked DV, but Kevin arrived in time to stop her from carrying out her threat to kill DV. On November 22, DV was shot in the head. Right before DV slipped into a coma, he accused Scott of firing the lethal bullet. Kevin and Eve worked together to clear Scott's name. On December 3, Kevin and Eve were able to uncover that Officer Gordon had framed Scott for DV's shooting. DV had once again regained consciousness, but his condition remained grave. Scott revealed that he'd been cleared of all charges then delivered the final blow when he told DV that blood tests had confirmed that DV was Scott's biological father.

On February 25, 2000, Kevin was struck from behind as he arrived at a church for the christening of Lucy and Scott Baldwin's adopted daughter, Christina Gail Baldwin. A woman wearing a long brown wig dragged Kevin's body into the choir room then plunged a knife into his chest. Eve found Kevin and frantically worked to save his life. Kevin was taken to the hospital and rushed into surgery. The would-be killer appeared to be Julie Devlin, a woman who had been brainwashed by Greg Cooper to aid him in the General Homicide murders. Julie was arrested, and she denied that she had attacked Kevin, but a videotape of the attack sealed Julie's fate.

Kevin survived the murder attempt, but he lingered in a coma. When Kevin woke up, he revealed that Greg Cooper, dressed as Julie, had attacked him. Rachel Locke, Julie's psychiatrist and Kevin's work rival, felt vindicated in her assessment of Julie, but Kevin continued to have doubts about Julie's deprograming and improved mental health. On April 3, 2000, Kevin was reinstated back at General Hospital. Rachel was not pleased, so she decided to run for a spot on the hospital's board. A few days later, on April 14, Eve proposed marriage to Kevin, and he accepted.

On May 19, 2000, Kevin and Eve exchanged vows, but their wedding did not go off without a hitch. Estelle Reese, the mother of Kevin's ex-lover Grace, created a scene when she accused Kevin of killing her daughter. Kevin was shocked when Rachel showed up to calm her mother because he hadn't known until that moment that Rachel had been Grace's sister. Sadly, Kevin's marriage to Eve was not fated to last, as a handsome new doctor named Ian Thornhart snagged Eve's attention.

Kevin found himself leaning on Lucy for support, and he threw himself into his work. Kevin began treating a young woman named "Charlie" who had been struggling with recurring nightmares of drowning. When Rachel got wind that Kevin had been treating a "girl" in a hotel room, she reported him to the board for unethical conduct. However, Rachel was the one in for a surprise because "Charlie" was her daughter, Livvie. Livvie had been in town, spying on her mother, but she liked Kevin and refused to testify against him.

On October 23, 2000, Lucy told Kevin that a DNA test had confirmed that he was Livvie's biological father and that Grace, rather than Rachel, had been Livvie's mother. However, Kevin opted to lie when he realized how deeply the news upset Livvie. He told his daughter that the DNA test had been a mistake, but he revealed the truth to Eve. The matter became moot when Rachel snapped and was revealed to be the person responsible for several deaths around the hospital. Livvie learned the truth about her adoption and her biological father. Rachel was apprehended and transferred to a facility for the criminally insane.

By April 2001, Kevin and Eve were separated, and each had moved on to new relationships. Kevin relied heavily on Lucy's friendship as she helped him become adjusted to being a father. He and Lucy got engaged again, but dark forces were at work when a priest named Father Michael Morley arrived in town.

Lucy learned that she was a descendant of vampire slayers, and she was determined to rid the town of vampires, starting with musician Caleb Morley. For a time, Kevin joined Lucy in her crusade to protect the town. They believed they had banished Caleb, but they were unaware he was still causing havoc. Caleb planted doubts in Lucy's mind about Kevin's love and fidelity, which drove her into the arms of Ian Thornhart. Despite Lucy's indiscretion with Ian, Kevin forgave her, and he surprised Lucy with a wedding on December 26, 2001. As a wedding gift, Kevin reunited Lucy with her adopted daughter, Christina.

The transition to married life was not a smooth one, as shortly after the wedding, Kevin's friend Paige Smith arrived in town and moved into the lighthouse with Lucy and Kevin. Lucy was suspicious of Paige's intentions toward Kevin. When Paige vanished while she was supposed to be watching Christina, Kevin and Lucy pieced together that Paige was actually an angel that had returned to earth to complete some unfinished business. Paige had been sent to save her relative Alison Barrington.

On April 1, 2002, Eve was killed in a car accident as she lost control of her car on a slick bridge. Kevin was devastated by his ex-wife's tragic death, and he felt bad for the young son that she had left behind with her new husband, Ian. Kevin leaned on Lucy. Around the same time, Kevin made an appearance on General Hospital to honor Audrey Hardy. Meanwhile, Alison had started a candle business, despite Livvie's objections that candles were associated with witchcraft. Shortly afterwards, Kevin made contact with the spirit of Rebecca Barrington, and he vanished.

Alison was charged with Kevin's murder, although Kevin was alive in Rebecca's world called Barnadoon. Lucy refused to believe that her "Doc" was gone, and she was able to channel him via Ian. However, Lucy stopped her contact with Kevin once she realized the toll that it had taken on Ian. Lucy helped Rebecca's spirit rest by clearing her name, and Kevin was free of Rebecca, but he remained trapped in the other world. He sent Lucy a message in the form of a dated portrait of her to restore her faith in him and their love. Lucy's cousin Rafe, an angel, intervened and lit a special candle that returned Kevin home to Lucy.

Once Kevin and Lucy were reunited, they were pulled apart over their dispute over which woman Rafe should be with. Lucy believed that Rafe's true love was Alison, whereas Kevin believed that Rafe and Livvie were destined to be together. Kevin had a change of heart when he found proof that Livvie had lied about the paternity of her unborn child to keep Rafe. Kevin went to confront his daughter, but Livvie mistook him for someone else and injected him with a psychotropic drug. Kevin assumed the personality of his dead twin Ryan, and he seduced Lucy. After, "Ryan" tried to kill Lucy and hurt Alison, which prompted Lucy to have him committed to a psychiatric care center. It was also revealed that he had assaulted a prostitute on Jasmine Island -- the place Kevin had retreated to after being injected.

On January 2, 2003, Kevin learned that his beloved daughter, Livvie, had drowned. Kevin was devastated by the death of his daughter, and his marriage to Lucy was over. Lucy had fallen in love with Ian.

On July 16, 2004, Kevin visited the Quartermaine home with Lucy to attend the memorial service for Lila Quartermaine. Lucy wore a red dress in honor of Lila because Lila had been the only person to offer kind words about the red wedding dress that Lucy had worn on the day that Lucy and Alan had wed. Lila had shared that it had been her favorite wedding -- besides Lila's to Edward. Kevin commented that he had considered Lila the sanest person, besides himself, that he had ever met.

On January 30, 2013 Kevin arrived at the police station because Alexis Davis had reached out to him about Lucy. Lucy had stabbed Detective John McBain because she had mistaken him for vampire Caleb Morley. Lucy had also mistaken Sam McCall for Kevin's daughter, Livvie. According to Kevin, Lucy had been suffering from delusions of a world filled with vampires, angels, and seers. He also clarified that he did not have a daughter named Livvie; she had been a part of Lucy's fantasy. Kevin added that things had reached a point where he had feared for the safety of "the children" (presumably Serena and Christina Baldwin), so he had packed them up, and he had left town.

Later, Kevin paid Lucy a visit at Ferncliff. He was disappointed that she still believed in her alternate universe, but he was happy that Lucy was finally receiving treatment. On February 4, Kevin met Mac and Felicia at the Floating Rib. Kevin confided that he loved Lucy, but Lucy's delusions about vampires had been the end of their marriage. Kevin acknowledged that the success of Lucy's cosmetics business had helped the madness "recede" for a time, prompting Felicia to speculate that Lucy's financial troubles had triggered the relapse.

Lucy slowly got better, and she and Kevin tried to make their marriage work one last time, but Lucy found herself repeatedly drawn to Scott. By December 2013, Lucy had moved out, and she and Scott had become lovers. Lucy felt guilty, but Scott reminded her that she'd been sleeping on the sofa, and Kevin had disappeared for weeks at a time. Meanwhile, Kevin was busy building up his practice at the hospital, and he had started to treat Franco Baldwin. Kevin was fascinated by Franco's case because Franco had once been a serial killer who had suffered from a brain tumor that had driven his murderous impulses.

During 2014, Kevin and Lucy tried to reconcile, but when Kevin caught Lucy and Scott in a passionate kiss during the Nurses Ball, Kevin called it quits for the final time. Kevin focused on his growing practice and was always on hand when his services were needed. In 2015, Kevin began to work with colleague Dr. Andre Maddox and would occasionally refer patients to the new doctor.

On April 14, 2016, Kevin had an unexpected encounter with Laura Webber at Metro Court Restaurant. Laura had reached out to "Dr. K" because she had needed a cryptologist to help her decipher clues that Helena Cassadine had bequeathed to Laura. Kevin revealed that cryptography was his "side passion," but it was quickly clear to Laura that Kevin was an expert. Sparks flew between the two, and a romance quickly blossomed. Kevin was with Laura in July 2016 when her eldest child, Nikolas Cassadine, was coldly murdered by his diabolical Uncle Valentin Cassadine. During the hostage crisis, Kevin had valiantly taken a bullet in the shoulder that had been intended for Laura.

On November 1, 2017, Kevin and Laura became engaged, but it was a short engagement. The following month, on Christmas Eve, Kevin and Laura exchanged vows, surrounded by their loved ones. Lucy conceded that Laura made Kevin happy, and she reluctantly wished the couple well. Kevin and Laura settled into life as a married couple, raising Laura's orphaned grandson, Spencer Cassadine. However, despite Kevin's skill as a psychiatrist, Kevin and Laura were unable to help Spencer let go of his anger at Valentin for Valentin's role in Nikolas' murder.

Compounding Spencer's grief was the knowledge that Valentin had taken up residence on Spoon Island because the corrupt Greek police had determined that Valentin had shot Nikolas in self-defense. For Spencer's peace of mind -- and safety -- Laura and Kevin agreed that Spencer should attend boarding school in Europe at an exclusive school with top-notch security. With Kevin's support, Laura decided to run for mayor, but she was forced to withdraw when she received word that Spencer had been injured in a skiing accident.

On January 19, 2018, Laura announced that she had to fly to France to nurse Spencer back to health. Her grandson had broken both of his legs. Kevin assured Laura that he understood, and he promised to reschedule his appointments so that he could visit her periodically until Spencer was well. Laura was grateful for her husband's love and support. Kevin and Laura maintained their long-distance relationship while Kevin focused on his research into the mind of a serial killer.

In June 2018, Kevin began to treat Carly Corinthos when she was admitted to Ferncliff for attempting to murder Nelle Hayes. Nelle had set Carly up, and Carly had pretended to have a breakdown to avoid being sent to Pentonville. Kevin had compassion for Carly's situation, and he suggested that they use the time to deal with her grief over losing her son. However, Carly became intrigued with the patient in the room next to her because the patient had been banging on the wall, tapping out an SOS message in Morse Code.

Alarmed, Kevin warned Carly to ignore the patient because the man was a dangerous homicidal maniac. Carly wanted to know more about the man, but Kevin refused to share any details. On August 23, Kevin paid the patient a visit to wish him a happy birthday. It was his twin, Ryan Chamberlain. Ryan had been confined to a straitjacket and appeared to be calm.

On August 28, 2018, Kevin made the mistake of turning his back on his brother during a visit. Ryan managed to free himself from the straitjacket then knocked Kevin out. When Kevin woke up, Ryan was wearing Kevin's suit, and Kevin had been confined to the straitjacket. Ryan instructed the orderly to sedate Kevin then strolled out of Ferncliff and assumed Kevin's identity. Ryan would periodically visit his twin to torture Kevin with threats and ominous updates about loved ones. Ryan made certain that Kevin remained heavily sedated during that time.

On January 21, 2019, Kevin suffered an intense migraine that left him blind. Ryan explained that the blindness was the result of a virus, but he refused to get his brother treatment because he couldn't risk anyone finding Kevin. Unfortunately, Ryan hadn't counted on Laura's persistence because she had long sensed that something had been off with "Kevin." On February 18, Laura followed "Kevin" to Ferncliff and was stunned when she saw her husband locked up in one of the rooms.

Ryan jabbed Laura with a sedative then dragged her and Kevin to the basement. After Ryan locked Kevin and Laura in a small room, Kevin happily reunited with his wife. They worked together, and with Kevin's knowledge of cryptography, found a secret passage out. After Laura escaped, she notified the authorities, and Kevin was taken to GH for treatment. On March 13, Kevin's vision had been restored, and Laura sat down with him to ask how Ryan had ended up alive and in Ferncliff.

Kevin admitted that the DVX had contacted him in May 2018 about an agent who had suffered a psychotic break. Kevin had been shocked to discover that the agent had been his twin. Kevin had realized that the DVX would have terminated Ryan if Kevin had refused to take him, so Kevin had transferred Ryan to Ferncliff. After several months, Kevin had found a drug combination that had taken the edge off of Ryan's madness, and Ryan had revealed that he'd escaped the explosion at the fun house and had worked for the DVX until Kevin had found him.

Laura was uncertain if she could forgive Kevin for keeping the secret because people had died. Kevin loved Laura, but he understood why she was conflicted. Kevin had had several uncomfortable encounters with the people that Ryan had victimized, including the mother of one of the murder victims. On March 22, Griffin Munro, the lover of one of Ryan's victims, assaulted Kevin on the piers. Kevin refused to press charges against Griffin for the attack.

However, Kevin quickly found himself in hot water when the district attorney decided to charge Kevin for his role in Ryan's murder spree. A couple of days later, Laura visited Kevin at the police station. She admitted that she wasn't ready to divorce him, but she also wasn't ready to reconcile.

On April 1, Nora Buchanan arrived from Llanview, PA, to represent Kevin. Lucy showed up to support Kevin as he fought the charges, but Kevin revealed that he had retained Nora in the hopes that she could get him a lenient sentence because he intended to plead guilty. Nora and Lucy insisted that Kevin was not responsible for his brother's actions, prompting Kevin to plead not guilty. Kevin was surprised that his bail had been posted, so he thanked Lucy, but she admitted that he hadn't paid for it. Laura had made the arrangements.