Is it permissible for a woman who wears the niqab to remove it in front of her husband's brothers and his son, and is it permissible to remove it during a trial period?

It is not permissible for a woman to remove her niqab in front of her husband's brothers or other non-mahram men, because they are not mahram. She is not to obey her husband in this matter, for there is no obedience to a creature in disobedience to the Creator.