Need urgent help

My greatgrandfather had a property of 10 acres which was passed onto his 3 sons [Including my grandfather] 40 years back.The name on Property card were of his 3 sons only though he has 2 daughter but he passed on the land to the sons. Now,i came to know about this land just recently when my grandfather died without a will,my father mother has died too. Now this is the case My greatgrandfather has 3 sons and 2 daughters as mentioned above - 1]1st son [My grandfather] 'X' [dead]- has 2 sons [out of which my father died] and then me and my brother are his heirs 2]2nd son 'Y' [dead]- has 2 sons 3]3rd son 'Z' [alive]- has 2 sons 4] 1st daughter 'A' [alive] - has 3 sons [out of which 1 is dead and his heir is his son who is local corporator] 5]2nd daughter 'B' [dead] - 1 son as mentioned,as to my knowledge on the property card there were only 3 names that of my grandfather and his two brother. Recently i came to know that some illegal activities were carried out on that land by some of my family members along in company with local MLA I went to check property cards in city survey and i was shocked - Now the Property cards has following names - 1] 2 sons of 'Y' 2]Grandson of 'A' who is a local corporator 3]3rd son 'Z' 4]our Local MLA IT is clear that the MLA and the corporator has put their names illegally and i came to know that this has all happened with support from 3rd son 'Z' and 2 sons of 'Y'.They have mutually agreed upon some deal which i am not aware.the name of my grandfather was removed illegally. I have no support in my back,this people are very strong and powerful and enjoys support of city survey officers,municipal corporation since they are in power. What are my choice ? what can i do ? when i talked to the sons of 'Y' in relation to this property he has said to me that there is no such property.and he is ignoring me.I came to know they are planning to build huge complex towers in said land since the MLA and corportor is builder..and have agreed to give [3rd son 'Z' and two sons of 'Y'] Thier share. what can i do ? I have tried a advocate but he is not helping since the opponents the MLA and corporator are strong.