I am invading as usual, but hey, I might be helpful!

At age 4, who knows? I didn't tell my parents "hey! NO! I am a girl!". I was just me, I didn't even know what the difference is!!!
As I grew up I just tried to fit in and slowly realized what's happening which led to age 17-18 where I learnt there is a way to change my body to fit me and to be able to fit as who I am supposed to be and not be forced be something else.
Seriously though, until teens I probably didn't understand what's happening around me and only then started wishing I was a girl, even then I didn't know it was possible and only learnt heard of people later but thought they look a bit weird and decided to pass. Only at about age 17-18 I realized it is possible to do it without looking like a trans and also figured I have to go for it no matter what. Turns out I was lucky, yey |
So in conclusion. No. If you don't say "mom I am a boy" at age 4, 5, 6 or even 20, it doesn't mean you are not a boy.
You only know yourself what you truly here. I know that at young age I acted girly and fitted well with girls since ever, my brother told me to stop doing this and that because it is like a girl, yet I never realized back then that I wanted to be one, I was simply being me not realizing there is much of a difference at all.
Even if we go to puberty and don't say it, it doesn't mean you are not a boy, I mean, we try to fit in, we know that's what people are since ever and we rarely think we can just jump over. Even if we might, we could be afraid to say it or fail to realize it.
But I believe people usually just try to fit in and it takes time to realize what they got into and what they should really do or even what they really want to do.