Is that the commonality with both sexes, or just with women?
I would think the primary motivating factor for male homosexuals would be the desire for unlimited promiscuity.
“...the desire for unlimited promiscuity” is what makes a homosexual lifestyle difficult for men to reject, but it isn’t the cause of homosexuality.
See: Hypersexuality; Etiology (Wikipedia) - http://en.wikipedia.org/wiki/Hypersexuality