Require suggestion

Hire a lawyer ask him to file as many cases as he can in different places against your brother wife and her family. Ask lawyer to take dates at short intervals. Let them roam court on different dates at different places. For filing any case you dnt need evidence. Till evidence stage come they will fed up in roaming court and come for MCD on your brother's terms and conditions. Your wife and mother can file DV. In 498a get AB. Once your brother get AB almost case solve. Your brother wife has filed case her duty to prove allegation not your family to prove innocence. Let your brother wife roam court.

Another prespective; Involve elders and anyone you trust, agree on MCD and end the matter.