When I was about 12, just about at the start of puberty, I found some family nudist magazines my dad had hidden away. Men, women, boys and girls doing completely nonsexual stuff. Camping out, swimming cooking hod dogs and playing volley ball. But I was hooked from that point on. Then I imagined that some of the boys and men were castrated or nullified and the mere thought was almost enough to send me over the edge.
I should add the my interest (not quite an obsession) in castration has always been a fantasy. The very last thing I'd want in real life is to be cut.