You are lucky boy, lol. Till the age of 12 I thought girls have male genitals too. First time I saw a naked girl, my patterns were interrupted, brain refused to accept the reality of the situation and I didn't have anything else to do apart from falling into denialism. Knowledge I gained skimming through medical books helped me to confront denialism to some degree. Finally, all doubts disappeared at 13 when my schoolmate showed me a p*rn video. It was disgusting, but pleasantly fascinating at the same time, I must say...
Thanks to my conservative parents, sex-related subjects were always prohibited and punished in my family. I am sure it's impacted me in a negative way. There must be a strong positive correlation between proper sexual education and mental maturity.