In my opinion...it's the illicitnesses more than the act. I doubt highly that if anyone actually experienced this, they would actively search it out on a regular basis or have it such.
Same for the forum, we the voyeurs and commenters can step in....then step out - without anything more than the fantasy of it all.
I do not have any experience here but of course have the fantasy of the twins. Even Coors Light can make it a household thing.
Mom/Dad/Sister/Brother - nope.
All of "morality" is culturally imposed, and only as real as the individual makes it, IMO.
That's not to say that I'm personally immune, we all carry cultural crap to one degree or another, but at the same time, I know this to be the source of judgement, and judgement is detrimental to us all.
....Was that too heavy? Sorry.
Alaine in Ft. Worth says mother/daughter isn't available because her daughter is now living out of state.
She used the word "routine", from which I infer that this is a fulfilled fantasy situation as some posters have suggested, not reality.