Gender Identity and sexual orientation are independent of one another even though the sexual component is very much a part of one's gender identity and vice versa. Also gender socialization is different from culture to culture and then changes when exposed to a new host culture. That is to say that gender and the perception thereof change for each culture. Plus society continues to change. Back in the 30s a woman wearing trousers in a film was a HUGE deal and now, not so much. Going back to the part of where gender changes from one culture to the next and then has to deal with host cultures. African American men and women are socialized in a far different way than the dominant white culture here in the U.S. So not only do they see gender in a bit of a different way in which the have been taught and perceive their role to be but they also have to deal with the fact that their ways do not exactly synch to the current dominant culture.
Of course other, more exotic cultures have been noted. One study listed several cross-cultural supernumerary gender precedents. In the Native American Two-Spirit traditions you have the Lakota Winkte, the Navaho Nadle, and the North Piegan Manly Hearts. There are also the Hindu Tantric and Hijra sects, the European Castrati, The Madagascar Sekrata, the Tahitian Mahu, and even the Islamic Xanith, Khawal, and Sufi traditions.
Now when we view the DSM guide there is one gender variant in which gender and sexuality plays a direct role in the diagnosis and that is transvestic fetishism (302.3). This diagnosis stands out because it states that the person must be male AND heterosexual in order to meet the definition.
Gender identity is something that most people do not think about nor focus on but that is changing as more and more studies examine the individual parts of the various cultures in societies like the US and the UK. Plus there seems to be a very serious attitude on the part of academics (and most certainly the corporate culture) in regards to the study of transgender and transsexual individuals.