How do children of 9 know they're gay?

[king1]

maybe it is a natural conclusion to be drawn by a nine year old boy these days, after all we all know that girls have girl germs until at least 12 or so... Therefore, not liking girls, you must be gay...

Now, this is a modern conclusion, because nothing seems to be taboo these days, whereas when I was that age, gay was kind of a taboo and a young nine year old boy back then was probably just lost and wondering where he fits in, until the girl germs were cured...