I have to disagree. I've known a few guys in grade school who were fruity even back then. They then grew up to be full blown homos (no pun intended, well,,,,maybe). You could pick em out even back then.
Yeah but that could still be their upfetchins. It doesn'r mean their attractions were determined by genetics.
But people of different types congregate towards groups that make them feel included. Black people tend to live near other black people. Same with whites. Just because someone may have a lack of testosterone than others doesn't necessarily make them gay..but sometimes societal pressures them into a group they feel most comfortable in. Be it lack of estrogen in women or testosterone in men....I don't think a hormone deficiency does/should dictate one's sexual orientation.
A boy might be effeminate but still straight. Some boys might lean a certain way, but up until recently most fought against it, hopefully overcame their urges and married women. Some teenagers, boys and girls, go through a confused phase, but until recently almost all grew out of it. That's not true anymore.
You describe the self-fulfilling prophecy. A boy has some characteristics that people think of as 'feminine,' so he is teased by kids and treated by his family in such a way that he becomes convinced he is gay.