I wasted 9 years of my life with a guy who said before we got married, that he wanted kids and that we would have them one day, but after it came through more and more that he doesn't really like kids all that much and he feels uncomfortable with them - and in the end he said, no, he does not want kids.
Anyway, we are divorcing now, living separate, and I live with my boyfriend and his 5 year old son. I am 39, not really completely too old to have kids, but I don't know right now.
Anyway, all I am saying is that even though the conversation should come up before you get really involved, it does not stop your boyfriend from saying just any random stuff to keep you 'happy'.