Denying sale deed by the seller

Dear Sir/Madam, I am with a person who is in deep trouble of land whereas there are two main parties involved one side the person who purchased the land and another side seller's entire family (Three Brothers A,B,C & Sisters) as per the passbook and other bond papers the buyer have received a Portion of land from X survey number for what he is entitled to and the seller is utilizing the other part of same survey number. Everything was good for few years. now when the buyer went for measurement of the land it is short and the short fall land is nothing but the Road which is in adjacent to the above said land and the portion of land which is he is occupied but now buyer is asking for justification from seller to show his land. Buyer is not ready do so, however seller claiming that buyer has to show the land to seller and the mediators of sellers are advising buyer to sacrifies the land which gone into the Road. whereas road was exist before this transaction. Over and above there is bias support by the political party to the seller & family and buyer is now help less with every day torture by seller's sisters like abusing and doing some dramas to influence to get in arguments. At last they are tying to make him run away from the existing possession. He went to the police, SI, DGP, Commision, Collector and they are also taking light and he seller is conducting many thretening activities to the buyers family. the buyer would have dialed police helpline number around 100 times but police never took the seller in custody even after producing all the original documents to police station. please advice what else he can do.