When his brother Robert left town to find Anna Devane, Mac agreed to care for Robert's and Anna's daughter Robin. At the time, Mac was dating Dominique Taub. However, being a full-time guardian to his niece left him little time for Dominique. She was unhappy that he didn't love her as much as she did him. So the two broke up.
Those Jones Girls
Later, Mac was involved with Felicia Jones. When Felicia went to Texas to care for her ill grandmother, Mac became the primary parent for Maxie and Georgie. It was a thankless role. Maxie was nothing but trouble - her sex life shown in graphic form over the Internet, underaged drinking, a drug overdose. He did his best. Maxie did enter adulthood alive. However, her mother went off chasing her husband Frisco, and didn't return to Port Charles until Maxie was on trial for the murder of Lisa Niles - years later. So it has all fallen to Matt.
Soon the good daughter, Georgie, was dating Dillon Quartermaine and causing problems for Mac as well. He tried to keep the two apart after Dillon and Georgie were found kissing in a motel room. Later on, he caught Dillon in Georgie's room, though Georgie claimed she and Dillon weren't having sex. However, that wasn't for lack of trying. Georgie rented a room at the Port Charles Hotel in order to consummate her relationship with Dillon. Mac found her there. He explained that he loved her and only wanted what was in her best interests. Georgie was quite affected by Mac's words and by how much he cared for her. She wound up not having sex with Dillon that night.
When it came to which man would walk her down the aisle, her father or her Uncle Mac, Robin had a decision to make. It goes to show how important Uncle Mac was in his niece's life. Her father, Robert Scorpio, was able to make it to the wedding, and he did escort Robin down the aisle.
Mac has gone through some horrific losses: Felicia leaving, Georgie's murder by the text message killer, the blow of Robin's death, and most recently, Maxie confessing to the murder of Lisa Niles and going to jail awaiting trial. Thankfully, she was protecting Matt Hunter, and the truth emerged.
Mac is certainly an eligible bachelor, but Molly Lansing's and Kristina Davis' attempts to fix him up with their mother, Alexis Davis, haven't worked out. The two are friends and could be more if something wasn't in the way. It could be that Mac is just too good for Alexis, who has been involved with Sonny Corinthos, Jerry Jacks, both of whom live on the edge, and formerly, she was involved with Ned Ashton, who was also rocker Eddie Maine. Mac seems very tame to her. Now Felicia is back, and it looks like that romance may be rekindled. And Mac will have more free time now. He's been replaced as police commissioner, and he's not unhappy about it. He's looking forward to enjoying the family he has left and having a life.