What is incumbent upon us to do regarding a sister who has strayed from the straight path, given that the father is aware of some details of her deviation yet has not taken action? Should he be informed of all the details? And what is the role assigned to the brother if the father does not act? Is the brother sinful in this case?

News must be verified before taking action. If it is proven that the sister committed what was attributed to her, then it is not permissible to leave her in this state. The father, in his capacity as guardian, must fulfill his responsibilities towards her. He must strive to use all means to protect her and prevent her from evil, including the matter of marriage if she is not married. If the father does not fulfill his duty, then the questioner should advise his sister kindly and remind her of God, and he may travel to her if he is able. And do not forget to frequently supplicate for her guidance.