If sexual orientation is genetic (a big "if") and since physical appearance is largely determined by heredity then it might make sense for gay people to have some physical characteristics in common.

Perhaps we're all ultimately related back to the only prehistoric bloke who really knew how to decorate his cave and add a nice garnish to the animal the tribe caught that day?

This would also explain the otherwise puzzling enduring popularity of "We Are Family" on the dance floors of gay clubs.