My guro fetish didn't start young, at least not that I can remember. I was always death-obsessed as a kid though. I'm going to blame it on my dad showing me video games with gibbing and movies with gore since essentially day one of my life, but I know that's not entirely to blame for me finding gore erotic. I currently find the screaming, pleading, and crying of women about to be raped/gored very hot, so maybe something I witnessed in my childhood had something to do with struggling.
I do know that my extreme interest in bunny girls started as a child. I hesitate to even call it a fetish at this point, it's more of an all-encompassing obsession that just so happens to be sexual sometimes. As a kid, I loved rabbits. I thought they were the cutest animal to ever exist in my litte world. And, as a result, I loved anything rabbit related. Fast forward a few years into prepubescense, and I get exposed to some of the character designs of Akira Toriyama, who also had a healthy love for girls with rabbit ears from what I can tell. In short, Dragon Quest and Dragon Ball gave me the curse of Toriyama.