The earliest memory I have of looking at another person sexually was one time when I was eleven years old and I looked up a picture of Daniel Radcliffe in Equus and after that looking up gay porn which appealed to me. I still liked girls romantically and all but I started masturbating to these sites. Could it be that because these were the first images my brain associated with sex it got wired into liking men? I mean, what if I'd looked up pictures of women instead and liked it by chance.
I don't think that would be a factor because the first kind of porn I watched was straight but i still have homosexual attractions.