A boy's chances of growing up gay increase with the number of older brothers he has, and the Canadian researcher who spotted the trend a decade ago now believes he is closer to explaining why: It all starts in the womb.
Brock University psychologist Anthony Bogaert first reported in 1996 the startling finding that a boy's probability of growing up gay increases by about one-third with each older brother in his family. It's a subtle phenomenon -- nearly all boys even in large families still grow up straight -- but subsequent research has affirmed that the "fraternal birth order effect" is real.
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