I have several varying ideas and always open to others:
Brother has always fantasized about his sister and then he finds this dream magic book that tells him how he can control his dreams and live out fantasies within them. So he fantasizes having a sex scene with his sister not realizing she is having the same dream. The Rp would involve a sex dream sequence and then their interactions afterward when they are awake. The dream comes as a surprise to her not realizing her brother magically manifesting the dream. She is confused by the dream, but it awakens her own sexual desires for him. She keeps having the dreams each night as they become more perverse until she decides she must talk to him about these dreams. She eventually tells him late one night when they are alone, which leads to making mutual confession of feelings, but he keeps it a secret about the dream magic. She hopes the affair will quell her feelings and it will be a one time thing, but it happens more than once. And then she finds out about the dream magic book... I am open to where this goes.
Hot New Step Dad
Daughter comes home from college to her mother's house for the summer and is mortified to find her recently divorced mom has hooked up with this hot young guy. Her mother is busy traveling a lot over the summer leaving her alone with him. She avoids him, but one night secretly spies him masturbating. She is simultaneously disgusted and turned on and finds herself thinking about him all the time. And then one drunken night they hook up and have the best sex of her life. I am open to how this goes.
Stalking fan abducts female celebrity and has her in a secret dungeon where he delusionally believes he can convince her to fell in love with him. At first she repulsed by the idea, but then she decides to play along in hopes of figuring out a way to escape.
I am open to where this goes.
The servant girl and the Prince
I am hoping for a nontraditional love story that involving a taboo paring. It gets complicated as he then has to marry, but still loves the girl he is forbidden to have.
PM with your ideas if you are interested in any of these.