Coy Mathis, left, plays with her sister Auri, 2, at their home in Fountain, Colo., Monday Feb. 25, 2013. Coy has been diagnosed with Gender Identity Disorder. Biologically, Coy, 6, is a boy, but to his parents, three sisters and brother, family members and the world, Coy is a transgender girl. Ideas about gender-disorders began to develop in the 1950s, and have been evolving ever since, both within the medical community, and in American society. (AP Photo/Brennan Linsley)