I hated children for a long time and categorically did not want them, but something changed.
I'm 18, I'm a lesbian, and I don't know if I want children. My friends, like, my age, would like children, but I... don't? I love my little brother, I love watching him grow up and teaching him, but I had to raise him when I was little, and because he has a mental retardation, it's hard for me. I had a difficult childhood myself, with mental health issues, so I don't think even at 30 I'd dare take such a step. I want to live completely on my own when he grows up. Maybe I'll have one child, I don't know... I've always wanted a big, strong family, but I don't even know what that means.
Upd: Thank you so much for your answers! I really felt like there was a clock hanging over me, or if I turned 25, everything would turn into pumpkins like in Cinderella, meaning I'd be too old for children. You've truly reassured me that I still have time.