Q: My brother married a non-Muslim who had a daughter from a previous marriage. They reverted to Islam and he adopted her daughter. Does the daughter have any rights to inherit from his estate?
A: This step daughter will not automatically inherit from him. If he wishes that she receive something after his demise, he can make a Wasiyyat (bequest) which must be less than a third of his estate.
Mufti Siraj Desai