There are some erotica writers who stick to one category, like gay or lesbian or BDSM because that is where they are most comfortable. They can write from a position of authority because of their expertise as a `practitioner’. Others attempt to write in a sub genre where practitioner expertise is impossible to gain, so it is fair game. Sex with wizards and alien races being obvious examples. Then there are those who choose to write about taboo subjects where gaining expertise is actually a criminal act. Bestiality can only be expressed within fantasy scenarios. The same goes for the other elephant in the room, incest. Perhaps because of the understandable pubic sensitivity on anything that may come close to paedophilia, mainstream publishers of erotica steer clear of incest stories, yet it is the bread and butter of on line free sites.
I wanted to see if it was possible to write a story in the incest category that would not make your mother throw up. I hit upon the idea of two adults falling in love and one knows they are related and wrestles with the moral dilemma of telling the other. What they choose to do with that knowledge is for two consenting adults to decide.