Well that makes it interesting that he'd ever marry Jen in the first place, unless she made her no kids decision after they got married. Love can conquer, well, some things, but one thing it cannot conquer is one person wanting children and one person not wanting children. No one who is ambivalent about having children should be pressured by a spouse into having them and no one who has the desire to be a parent should have to give that up because their spouse doesn't. You can agree no to talk about politics or religion if you have differing views, but kids, that's a deal breaker. Honestly, it should be one of the first things a couple talks about when they're getting serious.
I am one of those "crazy" women who never wanted children. When asked why I would honestly say that I don't like children. I understand their need to exist or we as a species would die out, but I don't want to be anywhere near them. Then they would always say the most disturbing thing ever "You'll feel different when you have your own."
Now, maybe I will, but what is that poor kids life going to be if I have it and still hate children? Why would you wish that on some theoretical child? WTF is wrong with people?
OK, rant over.
I totally agree with the assessment that Brad basically becomes whoever he is with so I could see him deciding he didn't actually want kids when his relationship with Jen was new and exciting and he was trying to get in her pants. But then Angie shows up and she's all "I want a zillion babies from all over the world" and Brad's biological clock started ringing so loud he couldn't do anything but pull Little Brad out and get cracking on making some babies!
He was the one who cheated, Angie was just stupid enough to think things would be different. Never marry a guy who cheated on his wife with you. No matter how special he says you are, and how magical his love for you is, in the beginning he said the same shit to her. If Jen knew he wanted kids when they got married and she didn't, then the score is: two stupid women and one stupid cheating asshole. No winners.