A perfect definition of the Third Sex given by a homosexual

"The third sex is described as a natural mixing or combination of the male and female natures to the point in which they can no longer be categorized as male or female in the traditional sense of the word. The example of mixing black and white paint can be used, wherein the resulting color, gray, in all its many shades, can no longer be considered either black or white although it is simply a combination of both"

-- By Amara Das Wilhelm, 'Tritiya-Prakriti: People of the Third Sex'

That is how homosexuals define themselves:

"People of the third sex are analyzed in the Kama Sutra and broken down into several categories that are still visible today and generally referred to as gay males and lesbians. They are typically characterized by a mixed male/female nature (i.e. effeminate males or masculine females) that can often be recognized within childhood and are identified by an inherent homosexual orientation that manifests at puberty. The homosexual behavior of these people is described in great detail within the eighth and ninth chapters of the second part of the Kama Sutra. While gay males and lesbians are the most prominent members of this category, it also includes other types of people such as transgenders and the intersexed."

-- Amara Das Wilhelm in 'Tritiya-Prakriti: People of the Third Sex'

Transgendered males are predominantly "heterosexual"

"Hirschfeld, the first serious student of cross-dressing, coined the term
"transvestitism" and indicated that the group was primarily heterosexual"

-- Bonnie Bullough, R.N., Ph.D.1 and Vern Bullough, R.N., Ph.D.2,3

(in her paper: Are transvestites necessarily heterosexual?"