Is this worth breaking up over?

I never thought I would want to have biological kids of my own - adoption or foster care was always my dream. But I've come to the reality that I will probably have to compromise on this issue if I want to get married.
I'm now almost 24, and my boyfriend of a year and a half and I recently talked about it, and having children of his own is a requirement for him when he gets married. Which is ok - but he also said he would not consider foster care, and only after some persuasion would he even try and pretend like adoption was a remote possibility.
I don't want to start a family anytime soon, but since we've talked about it, it seems like this could be a big issue in the future. We have a great relationship otherwise and he's a good guy - I want to brush this topic under the rug since it's not relevant yet, but if it IS going to be a big problem then maybe it would be easier to part ways before it gets harder to say goodbye...
It seems like jumping the gun by a LOT to consider this, but we already live together and I don't want to wait until we take the next step to have to confront it and realize we can't be compatible in this. Is it something to get the bottom of now or hold off on it?