Can we talk just a minute about the concerns your X has? (Understanding, of course, that there's a jealousy element here over your fiancee).
But putting that aside for a moment:
If there are guns in your fiancee's house, I understand your ex's concern. I wouldn't want my children in a house with guns either, especially if perhaps they are not secured adequately.
Also - having a teenaged girl in a house with a teenaged stepbrother is also a dicey proposition. They are NOT related, and pheromones being what they are, trouble might ensue. (When I was fifteen, my teenaged stepbrother came to spend the summer - trouble ensued.)
I'm not saying either of these things are necessarily dealbreakers, BUT dismissing them as just more craziness on the part of your ex is not really fair either. They are legitimate concerns that deserve to be addressed. And they might be reason enough for you and your fiancee to just keep dating until your kids are a bit older.
