I always thought a good story idea might be identical twins: one very conservative, the other a nudist. The conservative one has to go away for a trip, but can't afford to actually be away, so she asks her twin to replace her. Maybe she has a very strict college scholarship or something like that.
Anyways, the sister comes back, only to discover that her twin has created a brand new reputation for her. And worst of all, since they're identical, everyone's as good as seen her nude.
I've often thought a twins story would be very kinky and erotic. I know of a pair of girls growing up who "switched" but it was simply for a date. Nothing risque. I can imagine if it had gone further--not sure if the date would have realized or not!
I find it hard to stay in the story when the twins are made so different because most identical twins are similar even personality wise (the difference come in roles. Theres the "shy one" or "smart one" but only because someone else is less shy or smarter. They are both relatively both things.
Sex would be interesting though because they could have had very different guy experiences. Say one met a really great guy and they were long term so they had sex. Other twin hasnt yet because shes yet to meet the right guy.
Falls for a guy and they go out bunches but shes not ready yet and hes really in love with her so he wants to share that (hes had sex)
Sis and she talk about it and sis surrogates for the other twin. Nothing nutty but just enough to keep him feeling connected to his girl.
Cut to wedding night, WTF is going on here? We had sex how can you be a ...
All sorts of fun psychological issues to play with.
He thought he was with his girl, but wasnt so are they compatible.
All sorts of lying went down.
Did he marry her for the relationship parts or the sex? (so does he fall for the other sister now) Or is he essentially in love with HALF of TWO DIFFERENT WOMEN
Does the other sister wish she had the whole experience with this guy?
I think it works because they are still similar but slightly different due to life experience. So they would both likely get along with this guy in their respective ways. But in a way theyd have to be different too.
I seem to recall a story in the news a while back about an identical twin who used the fact that she looked the same as her sister to steal her sister's boyfriend. Definitely a rich vein.