[saden1]

Wow, here goes:

1. Seek happiness. There's no reason to be miserable.
2. Don't take the kids without the permission of the father. Doing so is bad in the eyes of the law no matter where you are. Those aren't your kids, those are her kids and the other guys kids.
3. Always stay classy and don't get yourself into trouble. You're no good fighting another dude and ending up in jail. If something happens while you're there by all means be a man, if not let the law deal with those kinds of matters.
4. If her husband wants to be a father to his children you'll have to get along with him. Also realize that those are his children first, you're the step dad at best, the guy who ruined their parents marriage at worst.
5. I don't know the full detail but it seems to me you want kids of your own. If you really want to have kids you should discuss this with her.
6. Taking risks is cool, taking sensible risk is better.
7. Stay cool with your ex-wife.

Good luck man.