Dowry harresment

My name is Naveen kumar and i am from Visakhapatnam we married our sister 7Years back to the people who are staying at kakinada we had given 1 acre land and some amount of money as a dowry my sister's inlaws are panchayat president of their village we thought that every thing is fine at my sisters home but slowly we came to that my sisters husband will daily come to home very late and that to in drunken state and he used to beat my sister daily it seems he always tell my sister to call my parents and ask for money and my sister is having two children's both are girls one is of 6years old and the other is 4years my sisters mother in law had taken all my sisters jewelery and now coming to point around 5months back my sisters husband came at night time in drunkened stage and he beat my sister very severely and told to her if she stays here then he will kill her by morning then she along with her children early morning came to vizag we cant able to see the blood marks on thigh of our sister the next day we took our sister along with some mediators to our sisters motherinlaws house and we scolded them they told sorry and they told that at present their son is not there we will call u when her son comes at last after frequent phone calls after 10 days they called and again we went my sisters husband told that he beat her in frustration and told sorry and he told that next time he will not repeat and thier parents told that we will see new house for them and we will call u then bring your daughter then we said ok and left the place now its around 7months pasted they not even calling and we are sending some family persons to them but they are prolonging that house was not taken now we are not in position what to do my sister is staying at our house along with her two childrens, can you people please guide us or advice us how to proceed in my sister's issue and how to solve this issue legally.