What a woman is obliged to do is to cover her hands and face in front of all non-mahram men, and avoid being alone with them, especially her relatives who are not mahrams, since because of their closeness fitnah (temptation) is likely to occur more rapidly than with others. It is more essential for her to cover in situations such as that which you asked about, where you live with your husband’s brothers in the same house. That is because mixing a great deal with non-mahrams weakens one’s modesty and makes one more likely to sin. If that is accompanied with uncovering the face and taking the matter of covering lightly, then it is more likely to lead to fitnah and sin. How many such incidents have occurred and families have been destroyed and family ties severed, because of carelessness in such situations.
The scholars of the Standing Committee were asked:
I am a man who is working and married, but due to my father’s health and financial situation we live in one house. Please note that I have two brothers, the youngest of whom is about 17 years old. What is your opinion on my wife and me staying with my father and brothers in one house?
There is nothing wrong with your brothers living with you in one house, so long as your wife is modest in her dress and wears hijab, and is not alone with either of your brothers in the house. End quote.
Fataawa al-Lajnah al-Daa’imah (19/366, 367).
And Allaah knows best.