Maybe in most cases, but when I was a kid I lived up the top of Fielding Lane and on a farm near us lived a farmer, his wife and thier two sons. One son was your typical strapping farm lad, the other, younger son was as gay as a lord. My mum was friends with the farmers wife and she told her that when the second son was born she really wanted a girl and for the first few years of his life he was basically brought up as a girl even to the point of wearing dresses and playing with girls toys. Could be just a coincidence but I'm not so sure.
See.
Genetics.
Some are born dimmer than others.

