The Kinsey reports also found that homosexual men reported larger penises than heterosexual men, which the reports claimed underscores the questionability of these studies and self-reported survey methods; however according to studies in prenatal hormones and sexual orientation, there have been studies linking particular hormones in the womb that predispose unborn male fetuses to both homosexuality and at the same time larger penis size.[40]
http://en.wikipedia.org/wiki/Human_penis_size#Environmental_influence_on_penis_size
In 'Race and Penis Size'.