Eh. Until the epilogue he spends most of the game complaining about abigail and jack, fantasizing about leaving them, and even goes into drunken rants about how he wants to kill abigail and she means nothing to him. His turn to family man felt to me like it came out of nowhere and he was only doing it cuz he felt obligated. Kinda soured me on their relationship, even if the proposal mission was nice
iirc, it was because Abigail had sex with almost all the guys in the gang, and John had some resentment about that, and didn't want to claim Jack as his own...then that one family abducted him and gave him to the mob boss, and John finally started to confront how he felt about Jack and Abigail, and acknowledged that he really did love them