The eminent Muslim scholar Sheikh `AbdelKhaliqHasan Ash-Shareef, a renowned scholar and Da`iyah, states: Every wife is required to cover in front of her husband’s siblings (brothers only) because they are not mahrams. As for the father of her husband, she can take her hijab off as he is one of her mahrams unless it is known that this father has bad manners or his reputation is not so good. In that case she must cover herself and she is not allowed at all to take her hijab off. She is commanded to cover in front of every mahram who is known to behave badly.