“…To our knowledge, 12 studies have investigated birth order and/or sibling sex ratio among gender dysphoric individuals (or their closest equivalents in non-Western cultures). Nine of these studies looked at differences in birth order and sibling sex ratio between “homosexual” and “non-homosexual” transsexual adults (Blanchard & Sheridan, 1992; Blanchard, Zucker, Cohen-Kettenis, Gooren, & Bailey, 1996; Gomez-Gil et al, 2011; Green, 2000; Poasa, Blanchard, & Zucker, 2004; Tsoi, Kok, & Long, 1977; VanderLaan & Vasey, 2011; Vasey & VanderLaan, 2007; Zucker, Blanchard, Kim, Pae, & Lee, 2007) (instead of “homosexual” transsexuals, we will refer to male-to-female transsexuals sexually attracted to men as androphilic MtFs, and to female-to-male transsexuals sexually attracted to women as gynephilic FtMs). Overall, these studies found an excess of brothers in the androphilic MtFs groups but not in the non-androphilic transsexual male groups.…”