Justice for wife

Hello Sir.. My sis aged 28 years married 6 years before she is having two kids elder one 4 and half years girl and younger 8 months boy.. my brother in law is having a love affair before marriage and continued even after marriage and pointing out my sis daily that i dont like u just for my parents sake i got married u like this even tough all these my sis has lived with him and going how use to beat her and mentally physically daily torcher.. because of his unwanted doings we went to police station for counseling in january after that he started his toucher more and doing a CID job on my sis and trying to make her get compromised divorce from her so that he want to be in safe side... because of his torcher 2 months before we said to come to my home with my sis and kids to speak but he left them on road and gone back to his parents place from that till today he is not listening any other words and now he is saying he want court letter from sis as he wont be responsible for anything my sis has is the responsible for all issues and my sis has to say sorry him in court itseems then only he accepts my sis and kids if not he dont need them.. how can move now how my sis can get justice to her life and kids too. he have lot of properties and having 20+lakhs package but he is very worst towards his family.. pls help and guide me