What is the ruling of the Sharia on a wife remaining in the same house as her husband's adult brother, without a mahram present, and what is the ruling on the husband's refusal to sell the house and provide separate accommodation for his wife?

It is the wife's right that her husband provide her with an independent dwelling that spares her the embarrassment of others observing her. If this is not feasible, then he can allocate a part of the house for her, independent with its facilities, if the house is spacious enough. The husband's brother is a stranger to her, and it is forbidden for him to enter upon her or to be in seclusion with her, because the fear of him is greater than that of others. The presence of another person with him does not permit seclusion, unless they are a group from whom the occurrence of indecency is unlikely due to their righteousness. The spouses must exchange rights and kindness. The husband is advised to urge his brother to work and seek sustenance.