Luke Spencer arrived in Port Charles in 1978. He has a long history of being involved with the mob. When he ran the Campus Disco, it was used as a front to launder money for Frank Smith, who ran the Port Charles Mob.
Years later, when Luke returned to Port Charles, he agreed to work for Frank Smith again to guarantee the safety of his family. Luke was to smuggle people into the country and his partner would be Frank’s lieutenant in Port Charles, Sonny Corinthos.
Luke and Sonny became close friends. Even thought Sonny was ordered to kill Luke, he refused. Sonny also promised Laura he would keep an eye out for Luke when they broke Frank Smith out of jail, because she was pregnant with Lulu. Sonny has always admired Luke for having a family, something Sonny has always wished for.
Sonny offered to be tested for a bone marrow transplant for a sick Lulu. Unfortunately, he was ineligible for testing because he had received a transfusion outside of a hospital (The transfusion from Brenda when he was shot in the Frank Smith breakout).
Sonny and Luke became business partners when Luke opened up Luke's Club. Luke was the front man and Sonny was the silent partner. They often confided in each other about their love lives, fathers, the mob life, and other issues that they had in common. They both respected each other. Luke was Sonny's best man at Lily's wedding.
Luke witnessed Lily being killed in a car bomb in front of Luke's Club.
Sonny and Luke remained close friends. For a while, they became estranged when Luke blamed Sonny for the death of Lucky in a warehouse fire. Even though it turned out to be the doings of Helena Cassadine, Luke ended their relationship for a while. Sonny and Luke became friends again when Luke realized it was not Sonny that was involved in the warehouse explosion and Lucky didn't die after all.
When Luke opened the Haunted Star, Sonny would often come by after hours to talk to Luke about things and they have remained close friends after all of these years.
*Sonny has confided in Luke about his stepfather.
*Sonny went camping one time with Luke and Lucky.
*Luke was the best man at Sonny’s wedding to Lily.