Done second marriage without taking divorce

Hi All, My sister got married in January 2013 in Araya Smaj in Hyderabad without informing any one in the family with my relation, the marriage was done by boy’s mother and sister and boys friends, even they are the relations they did not inform us regarding the marriage at any point of time. We recently got to know about the marriage after two years, my sister says she does not have any physical relation. She says that she went to marriage by forcefully and had done marriage in 1hr and came back to home as if she is going to college by same time. After known to us we thought of doing the marriage again to the same person because of not to get insulted in the society. But my sister says that his is not a good person and has many girls relations he always tried to s*xual have harassment but I never went with him. We spoke to their family members regarding it but they are supporting him which is false and says that girl only came to marry him (which is false if we see this is a preplanned by his sister and mother and his friends). He is used to do black mail my sis by putting the marriage certificate, photos and videos that I will show in your home and bring your family on the roads. We asked for divorce (mutual consent) but they are not willing to give. Recently my sister got second marraige, withought giving divorce. The person filed a complaint on us that we have done marriage withought second marriage without taking diovource. Due to some cirsumstances we have done marriage to our relation. we have spoken to him regarding divource to give. he was not willing to give us we have even spoken to their elder people even they are not wiling but asking us to convience my sis and send. The police has also scolded him that leave her and you do ur second marriage that would be better to ur life. but he want's to take grudg on us and making calls with higher management of police to SI to file FIR. previously 3 months back we have filed a case againest him before marriage that he has done marriage forcefully and threating my sister by their his family members. Please advise us how the case would be and how we need to come out of it, my sister is fine with the second marriage and doing well. Please help us for a girls life. The boy is big choor, he is fradulent runs back of girls tries to use them.