I just posted a story called "The Tribe." It's a fantasy, basically. It's about a large extended family that holds incestual orgies every month or so. I liked writing it a lot, as I was able to combine several fantasy elements, and use them in sex-positive ways. My particular favorite was the bukkake ritual. If you don't know about them, it was devised in Japan, supposedly to degrade the woman who's being coated with semen. In my story, though, the young lady is being honored, not degraded. It's a testimony to her desirability and readiness for sex.
The whole series will be about ritualistic sex being positive experiences for all concerned. I don't know if families like this really exist, but if they do, I sure would like to be a part of them!