My mother used to say that I kept her young. She & my dad had 7 kids. My oldest sister was born when they were 23 & 24. I was born when my mom was 44 & my dad was 45.
I don't have kids either and sometimes I forget that I'm not 20 anymore.
I think it's all about attitude & activity as to whether you "stay" young. Not about whether you have kids or not.