I'm a boy. That's just who I am, whether or not I have the right parts. Ken is still a man, even though his undies are empty, right? I just thought all girls secretly wanted to be boys, and felt their best when someone mistook them for one, right up until I said just that, and my family went "Uh, no." That's how much I took it for granted - that everyone felt this way, right? Because I'd never felt any different.
I can remember when I started liking diapers, however. It was a set time, a set day, and then it just never went away after that. I was... Four, maybe? Five?
One is a fetish, the other is my identity and my personality and my feeling of self. I didn't know I was trans before I knew I liked diapers, because I didn't even know I was trans. They're very much separate.