Wife family threatens

Sir, My brother had married in 2009 after thier marrige my brother's wife started creating disputes in family like a kind of taunting over her father and mother in law and not only this she was as not ready to take any responsibilities of the house even after asking. But this happened for few days and they left to another city as my brother works in different state. After few years her wife can back to stay as she was pregnant and needs mother in law support. My mom and dad supported with full dedication but her taunting remains continued on small matters daily. She started threatening her father and mother in law to leave the house in middle of night(she doen't have the guts to do so thats why she tries it in midnight so that everyone could easily threatened). After her delivery everything remain fine then her father started to threatened us for filing suit against us. For few years everything remain quite after the incident. But few month back when she was again pregnant she called her mother in law for taking care of her. My mother didn't want to but she did for her son but there they started taunting my mother every day for one month and also threatened them to take thier part of property from them. I have recoreded the voice of them when they were taunting and threatening her. I want to file suit against her and her father for threatening us for things not done by my family. What are provision available that could help us