I'm a child-free man. My best friend of 12 years is a mother of 2, and 10 years older than me. We're extremely similar people, with extremely similar interests. We just have completely different daily lives. I'd really struggle to think of her as not a peer. But my identification goes in the opposite direction - I identify more more older people. So it's possible you could find peers among 20-somethings?
For the record, it's not that I see _every_ person who has kids as "not a peer", just most of them. The few I do see as peers are by and large the people who had kids by accident and didn't spend their whole lives dreaming of being a parent.
