Divorce family matter

Sir, I am Binod from West Bengal. My sister has been married for 10 years and have a child (girl) studying in standard 2. There has been lot of violence after marriage since her husband is a very alcoholic person. There is never a day when he is not drunk. He drinks daily leading to family misunderstanding and problem within the family. There is violence daily in my sisters house. Fed up with this my sister left her home and went to Bangalore in search of a job. After 5 months she came back thinking that she will her husband might me aware of the fact that due to his drinking problem she is not able to stay in her house but the case is same, he is drunk always and says that he will not accept my sister. After lot of discussion my sister left the home and is staying with us. My brother is low is a govt job employee and my sister is unemployed. The child is with my brother in law. He says that he will file a divorce. Please help how to respond with the same and please advice any legal action to be taken against him. Regards