When I was in college, I wrote my thesis about enforcing clerical celibacy during the beginning of the Church to the 13th century (so you may see many postings about this topic). While I was doing research for my paper I read many great books (25 if I remember correctly), but there were a few that were my favorite as they contained the most interesting information that I had ever read. One of these snippets of knowledge that I gathered was that medieval people considered there to be three types of genders from Ruth Karras’ book (Sources).
As odd as it sounds, that is what they believed. Medieval people thought there were three: masculine, feminine, and chaste. Men played the active (masculine) role and women played the passive (feminine) role. The chaste category were those who gave up their want (desire) to have sex to live a life of devotion to God, so these included monks, nuns, sisters, and priests.
In medieval society sex and gender were intertwined so those who did not have a part to play in sex, either the masculine or feminine roles, were considered something else. Those who were chaste did not have any role to play as they were celibate (did not have sex). They thought there were three types of genders, because of the sexual roles that those individuals played.