Should him not wanting to have kids with you be a deal breaker?

If you want kids and he's done, then yeah, that's a deal breaker. As long as you have these feelings you will never be happy, and if you "accidentally" get pregnant he would not be happy. Either way it would be a serious wedge in your relationship, one that would probably break it up.

There are some things that you absolutely have to be on the same page about, and whether or not to have children is at the top of the list.

First of all, you're not really looking at it in a realistic way. Take his point of view and listen. One reason why he may not want another child is because he already has two with another woman, there's the detail, THEY AREN'T TOGETHER. He might be afraid that children will ruin the relationship, and thus leaving you behind. if he loves you so much, such fear will get in the way. Don't let this pass, but don't pressure him into it. He's doing what any other man would do, its worries that bring these thoughts. Stay with him, and don't mention children, or marriage. Chances are, if he DOES get married with you, the children concern will pass through, and you can get your chance. Think about it on your own time, ask him indirect questions like, "How did you feel when your kids were born?" or "What do you think is the best part of having a child?" Don't ask them frequently, it'll raise suspicions, but based on his answers you can get a 90% correct assumption of how he feels about this subject. Good Luck, and take in mind ^^ this is pretty easy, i'm only 13...

If you need anything else, don't be afraid to ask, a guy will assume that you're telling him everything, so he won't try to find out whats on your mind like you would with him. Once again, Good Luck, and i hope you two have a wonderful relationship.

Usually it's a deal breaker. He said he didn't want more, and if he gets more there will be resentment ..... on both sides....