The biggest question here is always why ?
Although it is not a fact that is true for all homosexuals, some male homosexuals share some behavior characteristics with females.
The same also applies when looking at female homosexuals.
Some "Butch" type lesbians exist. Some are extremely feminine.
The main differences in a male brain and a female brain can be found in the hypothalamus.
What is the really only characteristic difference between males and females when it comes to mating behavior is the preoptic hypothalamus.
The preoptic hypothalamus plays a role in the mating behavior exhibited by humans and other animals. It has 2 times the amount of cells in a male brain when compared to a female brain. This could have something to do with the increased sexual drive of males. But that is not all there is to know.
There is also a part that controls the biological clock.
The Suprachiasmatic nucleus. According to some researchers, this part is a piece of the puzzle when it comes to sexual orientation and perhaps what humans and other animals find sexual attractive.
Then there is the sexually dimorphic nucleus.
With heterosexual males this part of the hypothalamus is much larger than when compared to heterosexual females. The theory is that with homosexual males however, this part seems to be smaller as well.
Transsexuals, and then primary male to female transsexuals, have a smaller uncinate nucleus than when compared with heterosexual males who feel comfortable in their body. Also part of the hypothalamus. This part is smaller in size and neurons when compared.
Primarily, the sexual orientation and awareness is rooted in parts of the hypothalamus. It has to be, because in nature many "gay" animals can be found. And these do not have the neocortex and other parts that create the human conscience.