Please help my sister

My sister's husband (brother in law) always quarrels with my sister.Itz almost a year for their relationship and their happy moments are few.The problem is he listens to his elder n small brother.He will do whatever his brother says even in his personal life.He says directly to my sister that he love more than her and he ready to take divorce with my sister if his brother says to him.He always abuse her n my family infront of her n make her cry always.Again he scolds her for crying infront of him as e hate to see woman crying.Recently he had beaten her so she came home,after elders had a meeting n discussed the problem with my parents n his brother.After discussion our village elders came to a conclusion to sent her with him.They warned him not to beat my sister again.First one week he was fine and there after he started scolding my sister with more vulgar abuses than before.He do things in what way his brother directs n he even don't tell his income details to my sister.Upto he haven't what property he his having whenever we ask he keep pressure on my sister.Now my sister is my parents home as he was scolding her,even today he phone called her n started vulgar brother in law elder brother phone called to my father friend and warned him that with his political power he is going to jail all our supporters n our village elders who supported us including my dad and me. Please give us a suggestion to come out from this great trouble and to make my sister life happy again.....thank u very much in advance!