Jeet at Gene Expression links to a new study which discovers that female relatives of the mothers of male homosexuals produce more offspring. Thus a particular genetic predisposition manifests itself as homosexuality in a man and as increased fertility in a woman. Homosexuality is due to gene(s) which are (obviously) detrimental to a man's genetic fitness but are advantageous for his female relatives.
This would agree with my recent idea that a person's sexual orientation is a combination of masculinity/femininity genetic factors inherited from his/her parents.
Male homosexuals would thus tend to have more feminine parents. A more feminine mother would give birth to more children, both because she would be more attractive, and thus likely to be married early, but also because femininity is probably a good indication of a woman's reproductive health.
If this intuition is correct, then in layman's terms, if your wife's female relatives have big families, then on the up side there's an increased chance that you have a beautiful and fertile wife, but on the down side there is an increased chance that your son will be gay.