I must respectfully disagree. He's young; his life will change, and he may change with it.

For starters, the band probably isn't going to last. For all its glory, music is a very demanding and punishing industry. In his mid-twenties, my brother was in an incredibly dysfunctional indie rock band (of which I was an embarrassingly rabid fan) that had a hot stretch and got signed and played on The Late Show and toured America and Europe. The band eventually imploded under excessive substance abuse and the pressures of the road, and my brother is now an attorney and law professor and the devoted father of two young children, a man in his forties with very little resemblance to who(m?) he was at 26.

In the very off chance that my brother happens to read this: Sorry to make an example of you, bro, but this is a psychiatric support forum, I need you to make my argument, and nobody here takes what I say as fact. I love you.

Returning to topic: If the OP cares about the guy, it's only fair to both of them that she communicate clearly to him that her need to have kids is real and non-negotiable, and he has to decide whether his aversion to parenthood is temporary or permanent, given that it could cost him their relationship. If he still doesn't want kids forever, the OP has to choose between kids and him, and I don't envy her that kind of choice.

Then everybody has to decide that they trust each other.

My wife and I have always agreed during the sixteen years that we've been together that we would never have kids because she doesn't like kids and I'm a train wreck. If ever asked why we chose never to procreate, I answer that miscegenation is illegal under Halachic law, a response stupid enough to shut most people up.