For me, I knew at a really young age. As a child, I was always friends with other little girls and didn’t really care for boy stuff. My parents and older brothers often chastised me for “acting gay.” One of my aunts (not knowing that I really wanted to be a girl) once told me that if I could kiss my elbow, I would magically turn into a girl. I probably nearly broke my arm/neck on several occasions trying to do so.
I had plans when I was 17 to run away and change my identity and live the rest of my life as a girl. But “love” got in the way… that and twisted religious views. What I wouldn’t give to go back and change it all now and live as a girl from a young age. If only time travel were possible.