[QUOTE=red_awning]
Never put a love interest ahead of your child. Lesson learned.
[/QUOTE]
Wow, I can’t disagree with this more. Lesson learned? How does the fact that she played him have ANYTHING to do with him breaking plans with his child? 
More importantly, anybody in the OP’s position HAS to put that love interest (supposing it’s serious and committed) BEFORE the child. There’s an article that ran (in Redbook, I think), called “The Special Stresses of Second Marriages.” It concluded that the main reason second marriages are LESS successful than first marriages is that people REFUSE to put the new spouse “ahead of” the child.
The marriage suffers otherwise. For one thing, kids will split the parents, pitting the biological parent against the step to get what they want. My brother was in a yours-mine-ours marriage and I’ve heard plenty of horror stories. He’d tell “her” son that he wasn’t allowed to do something, he’d run to mommy and play the “Don’t you love me?” card, she’d undermine her husband, and you can imagine how it went from there.
For another, kids do grow up and move away and the parent will still be alone. There was a woman I knew in a divorce group who had a couple kids under 10 years old. She wanted to meet with some people for a movie or whatever and they started whining. She said, “I’ll stay home, if you don’t want to share me. But next time you want your friends over, maybe I’ll say, ‘No, I love you and I don’t want to share you…’” They got the message and gave her their blessing.
Corollary to that, the happier the parent is, the more he/she has to give her child emotionally. There was an excellent scene on “Knott’s Landing” or one of those night time soaps where Michelle Lee’s character was starting dating again. Her kids thought she was disrespecting their father’s memory. She finally broke down and said, “I loved your father very much, but he’s gone and I can’t bring him back. He made me feel so wonderful and I just want to feel that way again.” There you have it: people don’t exist solely as definitions of their relationships. She was a woman who had needs (redundant) and once they saw that, they couldn’t deny her pursuit of happiness…who would want a loved one to be unfulfilled?
People carry this to a pathological level. I think the genesis of it is, “I’m a single parent…who will protect my child if I don’t? What trauma has this divorce inflicted on my child?” Etc. I understand that but as the OP posts, dad needs a life too. What, is he supposed to be the bird in the cage that is there for the child 24/7 and his happiness is not an issue? The parent who feels that’s ok needs to look at the codependency issues in that parent-child relationship IMO.
I don’t know red_awning’s status (married/divorced/kids/etc.), but I hope that people who feel as red_awning would be clear. If you feel that your child will always come first, state that up front. It’s your life but people like me will thank you and move on.