I'm in this situation. I'm 31 and have never felt broody, have seen my sisters bring up their children and I would struggle to accept the restrictions that family life places on travel, leisure time etc. I'm far from being a high-earning career woman, I just enjoy the time I spend with friends, having hobbies in the evening and having lie-ins.
DH is 32 and goes gooey-eyed when he visits my niece and nephew and he's always said that he always expected to get married and have children. My own life plan was to grow old as a spinster - wasn't looking for a relationship at all when I met DH!
We will probably compromise by having just the one child. I quite like the idea of being a SAHM as I've enjoyed a bit of a gap in employment and I like being at home, I couldn't really justify it without being a mum really.
It's definitely the sort of thing that's a relationship deal-breaker. I've known quite a few couples who have split up after they agreed not to have children in their 30s but when they reached the 40s, the man decided he couldn't accept never having children and left quickly for a younger, fertile woman. I'd hate to be left in that situation in a decade, so I'm quite pragmatic about having a child because I think the relationship would be more fragile otherwise.