Brother of my Father has Taken over all the property.

Dear Sir, I have a query regarding the Property fraudulently taken over by my Father elder brother. My grandfather was a father of 2 Boys and 5 Girls. And he has a property in our city, After years 5 sister got married and living happily, however My father and His Elder Brother was staying in the same house, slowly elder brother started creating family problem and due to this my father has to left the house and started staying in separate rented home. At later date, my father Died in 1996 due to attack and before a year of my father death, my grandfather also died in 1995. Now we were staying in a separate home, Year gone, we have grown up, one point to add is my father has 3 daughter including me. Very younger daughter is mentally disabled. Now before a month we got to know that the elder brother of my father has started looking to sell the same property and he also has got someone who is ready to buy that property. When we came to know this thing, we have now decided to log a case against him in the court of law. However, we came to know that He (elder brother of my father) has already have a will with him return which he has got forcefully from my grandfather wherein he has not left any thing for us. as we are not aware in this regards, we are very much shocked due to this behaviour of this man. He has the "Mrutyu Patra" written by my grandfather and we know that he has done it forcefully. Now we have no choice left rather than going into the court. He has also mentioned that while taking over the property that he has sent the notice to all 5 sister but he has shown it this way that no one responded, but in the fact, no one has received any notice from him. And now he has taken over the property, our condition is too bad and along with that we have a sister who is mentally disabled. This property was under the name of my Grandfather hence do you think there is stand for our case in court? We think that this property was under the name of my grandfather’s Father but then we do not have proof or any document regarding the same. Do you suggest what can be done in this situation, will the INDIAN LAW able to help us. We are helpless currently and not finding anyway out. :( Thanks in advance for your advice and suggestion. Sonal.