Q: Please advise me on the following: Is a child (girl) allowed to stay with her step father and her mother in one house?
A: When the step-daughter becomes baaligh then she has to observe some sort of pardah with her step-father. She can live in the same house, but they must not be alone at any given time. And if the age gap between the two is not very big then full segregation must apply. And Allah knows best
