Genetics vs Environment... that debate has gone on for ages. It's a bit of both between for me. I was born with a bit more potential to be different but it was the environment that made that potential into a reality.
There were signs when I was a kid - I always had a "best" friend who was always a guy I really wasn't that close with. Most of my friends were girls. I was a bit nerdy, an introvert, and not into sports...
There was no dominant female figure, or an abusive uncle or cousin... no traumatic experience such as a heartbreak.
It was simply insecurity that pushed me to the other side. The unconscious admiration I had for other guys also made me look at myself and see that I wasn't as athletic, as good looking, as popular as these other guys.
I'm speaking as someone looking back here when I say that the insecurity I felt when I was younger somehow led me to believe that i was "less of a guy" and the desire I had to be "like" the other guys was somehow warped to feel like I "liked" other guys.
So years of that psychologic environment acted on the inborn potential... and here I am.... born out of insecurity. Unable to change what has been and unsure of what will be.