Is it permissible for the wife's mother to appear in front of the husband's brother, who lives with them, in clothes that are not revealing, knowing that everyone is an adult and the mother is over fifty?

If the wife's mother is one who is desired or desires men, then she must wear the full hijab in front of the husband's brother. However, if she is an old woman who is neither desired nor desires men, then she is permitted to uncover only her face and hands in front of non-mahram men, while being careful to avoid unlawful intermingling.