Blanchard and Zucker came to the general conclusion that birth order has some influence over sexual orientation in biological males in general, and homosexual male-to-female transsexuals in specific. This phenomenon is called the "fraternal birth order effect". In 2000 Richard Green wrote, "Homosexual male-to-female transsexuals have a later than expected birth order and more older brothers than other subgroups of male-to-female transsexuals. Each older brother increases the odds that a male transsexual is homosexual by 40%." Green did not find a higher incidence of homosexuality in the younger brothers of homosexual transsexuals.