I don't know if you purposefully looked for the worst possible version of that scenario, but you know that your sister could simply own this house she lives in, right? Why did you pick the worst case scenario, when there are like 20 more realistic and positive ones?
@FrenchPanda @Indyposterboy @Daojoan
Maybe their siblings are collossal jerks who would immediately kick the sister out at the slightest excuse?