All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
The husband has no right to compel his wife to live with anyone from his family, whether men or women. The wife has a the right for her husband to provide her with a suitable and independent accommodation as underlined in Fatwa 84608.
It should be noted that it is impermissible for the husband to accommodate his wife with a non-Mahram man in a dwelling with shared bathroom facilities, whether she gave her consent to it or refused. Therefore, it is impermissible for you and your sister to accept this situation and you should refuse accepting this man’s stay with you at your house.
You should also not accept his short stay as a guest even for a short time if it entails staying with him in seclusion in the absence of a Mahram.
For more benefit, kindly refer to Fatwa 181041.
Allaah Knows best.