There's MtF cross-dressing somewhere in the Rose of the Prophet series by Weis & Hickman but I don't know which book.

The best I could gather was that a character named Matthew takes on the alias Blossom.

Ask Ruskbyte if he can be more specific about which books in the Culture series by Iain M. Banks may deserve a place on this list. I only own two and don't know any better way to figure out which books in the series belong in this index.

Too understand this; you must understand that in the Culture, anything goes. There are no social taboos. Homosexuality is just as common as Heterosexuality, and just about everyone would be considered fully-fledged bisexuals. This stems mostly from the fact that Culture humans are capable of changing sex at will, not unlike Tonk's metamorphmagus abilities. The process, as described by Banks, is initiated by entering a trance-like state (presumable taught to them as children) and then setting their Residual Self Image (a term I borrow from the Matrix) from male to female, or the reverse. This causes their bodies to begin to change, over a period of about a year. The average Culture human will change gender and back at least once during their lifetime and will generally bare at least one child while living as a female.
-- Culture Shock, Chapter 4 by Ruskbyte

<Foone> and the disgaea novels have shas and kira: twins, and they both live in shas' body (because kira died)
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<Foone> as for Disgaea novels, I haven't read them. there's apparently 17 of them, they're light novels relating to the Diagaea series of videogames by Nippon Ichi Software.