How many gay men owe their sexual orientation to fraternal birth order?

Archives of Sexual Behavior,  February, 2002  by James M. Cantor

• E-mail
• Print
• Link

**********

James M. Cantor (1)

Ray Blanchard (1,2,5)

Andrew D. Paterson (2,3)

Anthony F. Bogaert (4)

Epidemiological studies have repeatedly shown that older brothers increase the probability of homosexuality in later-born males (Blanchard, 1997, 2001; Jones & Blanchard, 1998). Older sisters, in contrast, do not affect the sexual orientation of later-born males, and neither older brothers nor older sisters affect the sexual orientation of later-born females. Because females are essentially invisible to this process, we have called it the fraternal birth order effect.

The fraternal birth order effect has been demonstrated not only in ordinary ...