You don't seem to want to do the wrong thing again but in the end you might. You find this man attractive cos he is good with kids. How does this remind you of the first father when he wasn't even a good parent? And do you also find cheaters attractive? Also, have you sought his attention by flirting with him? I would leave this relationship too, particularly as it was Mark who was your friend, not his wife. If you fell in love with Mark, why aren't you with him? Sorry for all the questions, but I find your post confusing.