Filing case against Husband and family(Dowry & mental Harassment)

I have two sisters, Elder one was married 5 years ago. My younger sister was married 1 year ago, now in case of my younger sister the before marriage they have demanded 5 lac cash and I-20 car costing 8 lacs, and gold gifts for relatives(we have all relevant proofs for this), Somehow we managed to give it, but after two days of marriage, her husband and his family started to harass her saying that she did not bring anything, we tried for mutual consent to save the family for 8 months with regular sittings, but earlier they were saying that they want to save family, now they kicked her out of their house and her in-laws and husband is saying that they will not keep her with them, she is living with us from last 4 months now. My sister still don't want divorce. But her in-laws and husband are ready to fight the case. Moreover, He father in law already has case of corruption, which we came to know after her marriage that’s why he don’t get pension also he worked at a Govt. PSU and they are all dependent on my sister’s husband who is working as PO in a Nationalized bank. Now the other part of game they played is, he came in contact with my Elder sister’s husband during my younger sister’s marriage, he came to know that due to some medical issues of my sister they don’t have children, so after kicking my younger sister out of house, they started persuading my elder sister’s husband to leave her and saying that we got this much money, you didn’t got anything. They succeed to break a fight in my elder sister’s home and they are also following the same steps they did with my elder sister now. Now my elder sister parents in laws have thrown her out of the home and she is living in rented accommodation. Her husband has beaten her many times due to irrelevant reasons. He don’t go to the place she lives and he is living with his parents. We are in trouble being bitten from two sides. Please suggest what can be done.