Like everyone else has said so far, not everyone is the same. Everyone's story is different and it doesn't make them any less genuine if they aren't cookie cutter.
Some people don't even know what to call it. When I was 4, I felt like I shouldn't have been a girl, I actually cut my hair to make it shorter... I didn't know what to call it, I questioned whether I was a lesbian or not at one point because I like women. And when I was 15 I learned what it was called and I came out. So, not everyone who knew from a young age that they were born in the wrong body is bold and says, "I wanna be a boy!" or whatever. There is sometimes a questioning period, not everyone just blurts it out.
There are people like Elwood and a few others, who didn't realize it until later on. That doesn't make them any less genuine than someone who knew something was off at younger ages, in fact, some people who didn't know at younger ages might start to see the signs once they've come to realize they are transgender, sometimes they don't.
A lot about transition isn't about the hormones or surgeries, a lot of it is finding yourself and who you are. My suggestion to your friend is that he see a therapist to sort out what it really is. Maybe he's transgender, maybe he's not, but the best way to find out is to see a GID(gender identity disorder) therapist. And if he is ftm, he'll probably need to see one anyway to get hormones and surgeries if that's his intent.
