casino_king SG CLICK ANYWAHERE FOR LINK. Sexual orientation 'affected by number of older brothers' Alok Jha, science correspondent Tuesday June 27, 2006 The Guardian The more biological older brothers a man has, the greater the likelihood that he will be gay, according to scientists. The result suggests that a man's sexual orientation may be influenced by the conditions in his mother's womb when he was a foetus. Anthony Bogaert, a psychologist at Brock University in Canada, studied 944 heterosexual and homosexual men who had either biological or adopted or step brothers to try to work out whether a phenomenon known as the fraternal birth effect - where, on average, a higher number of older brothers correlates with a higher chance that a man is gay - is a result of social or biological mechanisms.