A great painter dies of cancer, and his second wife goes after a car accident shortly after. His first wife is excluded from the will for attempting to murder him, and the third died many years ago. His will has left his vast riches (estimated in millions) to the children of his three wives.
The first are two daughters of his first wife, both adults and successful business women.
The second is his second wifes son, barely out of highschool and very timid. He's shy and not good with girls.
Finally, the third wifes daughter, who is much more outgoing and playful, but barely halfway through sixteen and still in school.
They will only get this money if they can live 5 years in the mansion he left them. He wanted what was left of the family to come together.
What the two youngen's don't know is they're about to become lovers, as the two older sisters are also very naughty, and have many tools and plans for these two cuties, slowly breaking them into slave roles. Toys, bondage, cuddling, kissing, huggies, romance and all the other sugary and naughty stuff :) may even force the boy to be a maid and clean the house, or have them swap clothing, or make the girl wear a strap on and take her new partner.
Freeform. I'd take the role of the boy ^_^