Morgan Stone Corinthos is the son of Carly Corinthos Jacks and Sonny Corinthos. As a young child, he endured several break-ups and reconciliations between his parents. He resided primarily with his mother and had varying levels of contact with his father due to the threat of violence in Sonny's life. Despite the changes in custodial agreements, Morgan welcomed both his biological father and his step-father, Jasper Jacks, in his life.

Morgan spent time as a child with his older half-brother Michael and his older half-sister Kristina, but he was especially close to his cousin Molly Lansing due to their closeness in age. He also adored his younger sister Josslyn and willing spent time with her. Morgan's world was shaken during his youth after Michael was shot in the head and spent a year in a coma. When Michael did recover, his personality was not the same and Morgan struggled with the changes that had taken place with his brother.

After Michael had been shot, Carly prevented Morgan from having any contact with Sonny. Additional body guards were assigned and Morgan bonded with a particular bodyguard who was later revealed to be his oldest half-brother, Dante Falconeri. Morgan's life was rocked again when Carly and Jax separated and a bitter custody battle over Josslyn ensued. Jax attempted to kidnap Josslyn and Sonny intervened with a threat against Jax's life and he was presumed dead. Carly held Sonny responsible for Jax's "death" and sent Morgan away to a military school to ensure that Sonny would not be able to have any contact with him.

Eventually, Carly relented and allowed Sonny to periodically visit Morgan, but at a location far away from the military school, so that Sonny would not know where to find Morgan. As the years passed, Morgan stopped visiting with his parents, preferring to travel with friends in Europe during his school breaks.

In 2013, Carly and Sonny received word that Morgan was in trouble after accumulating several thousands of dollars of debt in an online gambling ring. Before Sonny or Carly made contact with Morgan, he left school to hide at his girlfriend's home. After Morgan had been worked over by thugs involved in the gambling ring, his family tracked him down and forced him to return home to Port Charles.

Morgan moved in with Michael and Morgan's girlfriend Kiki moved in as well shortly after. Although Kiki and Michael claimed to dislike the other, Morgan sensed an attraction between them. Soon after, Kiki was revealed to be a Quartermaine and Michael's first cousin. Morgan was pleased with the development as it ended any chance of romance between his brother and girlfriend. Together Morgan and Kiki took up residence at the Quartermaine mansion.

After the move, Morgan continued to question the feelings between Kiki and Michael. His fears were justified after he learned that Michael and Kiki had shared a kiss before they were revealed to be cousins. Morgan decided to fight for Kiki and stumbled upon the knowledge that Silas Clay, not Franco, was Kiki's father. Kiki's mother Ava confirmed that Michael and Kiki were not related and advised Morgan to keep the secret in order to protect his relationship. Morgan feared that the truth would eventually come out and proposed to Kiki. She accepted and Morgan hoped to marry her after a short engagement.

The truth regarding Kiki's paternity was publicly revealed and Morgan feared he would lose Kiki if she knew that she could be with Michael. Morgan made sure that Kiki did not know the truth and they married. Michael suspected that Morgan had rushed Kiki to the altar before she learned that she was not a Quartermaine. Morgan denied the accusation and the brothers bonded over their concern for Sonny following the death of his fiancé Connie Falconeri.

Morgan looked forward to celebrating his marriage after Ava and Sonny decided to throw a party recognizing the newlyweds. However, Sonny's mental health declined and he used the public event to announce that he had known that Kiki was not related to Michael because Morgan had told him before the wedding occurred. Morgan was crushed by his father's betrayal and lashed out at everyone in his family. Kiki declared the marriage to be over and Morgan found comfort in the arms of Kiki's mother Ava. After they spent the night together, several people discovered that Morgan had slept with Ava but he defended their relationship and insisted that they had done nothing wrong.

Morgan continued to sleep with Ava and moved in with her against the wishes of his parents. While living with Ava, Morgan overheard a conversation between Ava and her presumed deceased brother Julian in which they revealed their intent to bring down Sonny and his organization. Julian believed that Morgan needed to be eliminated after he realized that Morgan had overheard the private conversation. However, Morgan convinced Julian that he could be an asset and offered to help the Ava and Julian destroy his father.

Morgan used his personal connections to plant a listening device in Sonny's office and Sonny was devastated when he learned that his own son had sided with his enemy. Morgan remained committed to the Jerome family even after his family begged him to end his association with Ava and Julian. Instead, Morgan was pulled farther into the organization and joined Julian on a visit to Sonny's warehouse which turned into a shootout. Morgan held a gun on his father and Sonny immediately dropped his weapon while Sonny's longtime bodyguard Max approached. Morgan shot Max in the chest and was deeply shaken by his actions. Afterwards, Sonny ordered Morgan to help him care for Max until the ambulance arrived by Morgan left with Julian instead.

After Max's shooting, Morgan reconsidered his choice to work with Julian and tried to quit. Julian refused Morgan's resignation and threatened to harm his family if he walked away. Meanwhile, Sonny and Max covered Morgan's involvement in the shooting. Morgan was relieved when Sonny figured out the predicament he was in with Julian. Sonny worked to extricate Morgan from the Jerome organization but his assistance required that Morgan leave all of the Jerome family, including Ava, behind. Morgan pretended to comply but covertly continued the relationship until Sonny agreed to bring Ava into the Corinthos organization.

Morgan was pleased with Sonny's acceptance of Ava until he learned that Ava and Sonny had slept together. He was livid with both of them and accused his father and girlfriend of having a secret relationship behind his back. Ava and Sonny each swore that they had only been together one time and had immediately regretted their actions. Ava continually professed her love for Morgan and he considered taking her back even after she revealed that she was pregnant with either his child or Sonny's. However, Morgan claimed that he was done with Ava and his father for good after Ava moved in with Sonny.

As Morgan turned away from his father, Michael and Kiki offered their support. Through Michael's position at ELQ, Morgan was allowed to reside at the Brownstone in exchange for his help in the renovation of the building. Kiki joined the manual labor and moved in as well. Morgan and Kiki reconnected as friends and became closer after they stumbled onto the truth that Sonny had killed Michael's father A.J. Both Kiki and Morgan agreed not to tell Michael what they had learned. They also bonded over their concern for Ava and her unborn child.

When Michael learned the truth about A.J.'s death, he pushed away everyone that had lied to him, which included Morgan and Kiki. Around the same time, Ava's daughter Avery was kidnapped by Nina Clay. After Avery was located, she was placed in Kiki's care while both Ava and Sonny spent time in prison. Morgan was disappointed to learn that Avery was his sister instead of his daughter, but he remained a presence in her life even after Sonny was pardoned and took Avery home. When Michael chose to seek custody of Avery, Morgan sided with Sonny.

A judge awarded custody of Avery to Michael and he banned Kiki and Morgan from seeing their sister. This prompted Morgan and Kiki to switch out Michael's prescription medication with one that would impair his judgement. Their plan appeared to work but Avery was kidnapped as she was transferred out of Michael's care.