My sister in law and her family is harrasing my brother and my family

Hello sir It's been 6 years since my brother's marriage,they have 2 kids ,my sister in law mentally, physically, torturing my whole family even use abusive language with the support of her family ,my brother is very decent n she take advantage of it ,she don't even do any thing, doesn't take care of her kids my parents take care for their kids ,she wants to separate my brother from the family, openly says I'll put false alligation on you and your family in front of her family (my sister in laws family support her and give idea to her) her family also says we should send you into the jail even she cross her line and trying physically fight with my little sister and without any reason she doing all this things and my parents ignored so that there would no fight but now a days she's daily blackmailing my family that she will pretend to commit suicide and send every one in to a jail ,her mother, sister teaches her , sir please help our family and suggest what can we do as a family and what should my brother do? Please ? help us