Fraud transfer of Name

This case is about my father shop which is still there in Grant Road (Mumbai). My father have 2 wifes, but he used to stay with us I am the only son of 2nd wife, that’s why 1 wife and her children used to think that they will not going to get their share in shop that’s why they have fraudly transfer the name of shop owner under the name of 1st wife. In 2003 daughter of 1st wife get married and she visited to our home in 2004 for a signature in regards to the transfer of name for ration card, without checking papers my father have signed the papers on the trust of daughter. Due to shop was under renovation my father came to know after couple of years that the paper was signed that was not for name transfer of ration card, actually it was of transferring the name of shop owner. My father has fight with those people asking them to provide the original papers, but they have not handed the papers of shop till 2009. Even my father has visited to the lawyer for a resolution, so lawyer have asked him to sue a case against 420. But my father does not want to get into this matter, that's why he has started to handle this entire case by his own way. My father has tried his level best to get the paperback but unfortunately in 2009 my father passed away. All of our relatives know that they have done fraud but no one help me to get my rights. I request you to please advice that how I can get my rights.