Mc is a party play boy kind of guy. He's not the type to commit or take a relationship seriously.
his bestfriend got pregnant, the guy left her and she doesn't want her reputation to get tarnished because of 'reasons'(i forgot, it was related to her education/job/career)
so they get married, the guy fell in love with the daughter(non-sexual),he treated the daughter as his own.
I don't want to spoil anymore, things happened, they separated and girl gets custody of child, mc is devastated to be separated from his daughter. etc. etc.
I think he calls her 'little sweety' could be wrong.