Cruelty from husband and family

Sir, My Sister got married 8 years ago,it was a love marriage.She is having a daughter in this relation.The relation was good for the first five six years ,though small family problems were being there in between.But for the last two years her husband is behaving very rough to her and he doesn't even like her presence in his family.He is working at a small private bank where gold loans are provided.He is having indecent affairs with many ladies who are approaching him for loans and he is spending much time on mobiles and social medias to communicate with them for this filthy things..He has been caught many times on this issue by my sister and once by his brother's wife for long time filthy mobile talking at night time. Now the same behavior is continuing and last day there was a huge fight between them and it was for asking an indecent affair that he was having with their neighbor married lady. My sister got severely beaten and the neighbors involved in this matter and they have called my parents and asked them to go with her otherwise he will kill her. Now she is in our home and we are planning to file a case against him and family. Sir, more shocking fact is that he threaten his parents not to give any food to her and daughter.She didn't tell any of those things to us at any time.Now only all these things are coming out.She cooked her foods for herself and daughter , and she is not even allowed to use the cylinder for cooking....and these fights were usual happening in their life and this child is there in between them all time seeing those fights .. Sir can you please give an advice regarding this and what we can do at this stage.? Sir if you can e mail the reply it will be very thankful as the mobile is not allowed in our premises , I am working in kuwait as an accountant.