1) best option is for your brother and his wife to stay separate in rented flat near your parents residence
2) it would insulate you and your family members to some extent in case false DV case, dowry harassment case is filed
3)in the vent false dowry harassment case is filed apply for and obtain Ab from sessions court
4) your parents can obtain court order to direct brother and DIL to vacate portion of house in their possession and seek permanent injunction restraining them from disturbing their possession of the house