The major difference between me and my sisters was that I had no inclination to marry at a young age. I was out having way too much fun exploring the world and all its offerings. I finally married at one month shy of age 35 and had my one and only child at age 38.
If you've already committed to being child-free in your head and heart--that's okay-- but your partner needs to know long before the wedding or it's not fair to anyone. You need to be on the same page as your partner when it comes to these huge life decisions. Be real. Be mature. Share your truth.