Is it permissible for a woman who wears the niqab, but does not believe it to be obligatory, rather desirable, to wear the niqab outside the home and remove it in front of non-mahram men inside her home, such as her husband's brothers?

The most preponderant and authoritative opinion (fatwa) is that it is obligatory for a woman to cover her entire body, including her face and hands, in front of non-mahram men. This obligation is even more emphasized in front of her husband's relatives. However, for a woman who believes in the validity of the madhhab (school of thought) that holds the face and hands are not 'awrah (parts of the body that must be covered), there is no blame upon her for uncovering them, as long as she does not fear fitna (temptation or discord). Nevertheless, it is recommended for her to cover them in all circumstances, and men are obligated to lower their gaze from her.