I knew when I was still a brat myself that I didn't want brats because I didn't even like kids when I was one. But forced babysitting when I was 17-18 by my aunt absolutely cemented my choice. This is the same aunt I mentioned in another thread who would just dump her kid on unsuspecting relatives because she didn't want to mommy. I usually got left with the child on Saturday nights because my aunt was still trying to hide the fact she'd had a child (long story), so I'd get forced to watch her toddler while she went to church. There was nothing wrong with the kid, she was a perfectly normal toddler (she was also still in diapers), I just don't have patience with kids.
My older cousin never got forced to do it because she had a job and friends, and my younger male cousin "Ben" (not his real name) just had to say he didn't like the toddler cousin, which made her cry and then magically Ben never had to brat-sit. I always got stuck with it because I had no job, and it was assumed I had no friends and no life. Yeah no, I have nothing better or more interesting to do on a Saturday night at 18 than watch my aunt's ill-conceived child. Thankfully going off to school meant no more on-call brat care and my aunt had to actually watch her own damn kid.
In retrospect, I barely did much of anything, but those were some of the longest hours of my life and made me beyond certain that I never wanted to do that every fucking day. If I didn't even have the patience to deal with a normal child for an hour or two without wanting to slit my wrists, how the fuck would I ever deal with a child 24/7/365 for two decades? I wouldn't, that's how. And I was never naive enough to think any brat I produced would be different just because it's mine.
I knew I was CF before I knew the term "childfree" existed. I think I have shared this story before, but when I was like 7 or 8, I had one of those Baby Alive dolls where you spoon slop into its mouth and the same slop goes into its diaper a few minutes later. You know, to get girls ready for their "inevitable" destiny of being Moos.
Well I got tired of that shit in a hurry, so I fixed the needy baby doll by cramming Tootsie Rolls down its throat and up its ass. Ta-da! No more feeding and no more pooping! Yeah, I'd be a terrible parent.