Juan Santiago is the son of Lily Corinthos and Miguel Morez. His parents gave Juan up for adoption at the wishes of Lily's father, Hernando Rivera, who felt they were too young. Lily had always regretted her decision and wanted to make sure her child was happy with his adoptive family.
When Lily was killed, one of the first things that Sonny did was go to Puerto Rico. He took Juan to a park and told him the news of Lily’s death. He also gave him Lily’s cross, as well as the promise that if he ever needed anything at all, that Sonny would always take care of him.
Years later, Juan arrived in Port Charles. He had remembered Sonny’s visit with him and he thought he was his father. Sonny was very shaken when Juan arrived in Port Charles. He knew Lily would want him to take care of her beloved son. Juan wanted to work for Sonny and he refused. He didn’t think he could protect Juan and he pushed him away. He was too afraid he would hurt him.
Juan was severely beaten up by Sonny’s enemy, Joseph Sorel. Sonny blamed himself for what happened to Juan and kept vigil at his bedside. Sonny felt he had let Lily down because he wasn’t able to protect her son.
It wasn’t until Sonny explained how Lily was killed that Juan finally understood why he was so reluctant to have any type of relationship with him. They eventually established a cordial relationship and Sonny even helped to secretly finance Juan’s singing career.