I'm 42 and have known since I was 4 years old that I never wanted to be a mother. It's seriously one of my earliest memories - I didn't want to make my bed, my mother was exasperated with me and said "you'll be sad you treated me so badly when you have kids of your own"... and I remember being just appalled at the thought of being a parent.
I just don't enjoy children. I like peace, quiet, and order, and the freedom to do what I want without having to factor in children. Plus it looks super stressful to be a parent. I have 2 nephews and a niece, and while they're good kids, their parents always look so utterly exhausted and overwhelmed. And I'm definitely not good at being an aunt - interacting with children just doesn't come naturally to me.
Everyone told me I'd grow out of it. I had to fight to get my tubes tied in my mid-twenties (for real, I had to see so many doctors and had a botched Essure procedure at Planned Parenthood before I finally found an OBGYN who would take me seriously!).
No ~~regrets~~ rugrats!