I mostly write fantasy, and mostly with queer characters.
In my W-I-P, I recently decided it was the kind of world where anyone could have homosexual or heterosexual relationships, to varying degrees, at any given point in her/his life. Not exactly meaning that everyone is essentially bisexual, but because there's very little moral or religious restriction on sexual behavior; just some pressure to reproduce and carry on a family line.
The story started with -- what I thought was -- a very heterosexual male protagonist. I recently wrote a scene in which he receives a kiss from another guy, and he's thrown a bit by the feelings it produces in him. Just realizing that he *could be* sexually and maybe even romantically involved with another man, though those aren't the feelings that have shaped his view of himself.