Is it permissible for a woman to wear the niqab only outside the home, and remove it in front of her husband's unmarried male siblings if there is no fear of temptation from them?

Covering the face is obligatory for the wife in front of her husband's brothers and other non-mahram men. However, if she follows the opinion that deems it commendable (mustahabb), she is not obliged to cover it. Nonetheless, covering it is better, more absolving of responsibility, and further removed from causes of temptation. One must beware of family gatherings that involve unlawful mixing (ikhtilat).