Sucession of Property?

Hello to All, I am Samar from a village in Goa. My grandfather "A" has expired and he has several property plots in his name and there some plots in which he is co -owner with some other owners . My Grandfathers wife ie my grandmother also owns a plot as co-owner with some other owners. My grandfather had two daughters and two sons. The two daughters are married and staying in another villages for past 25 years. One of the daughter has a mentally challenged son & her husband. Other daughter has a son & daughter & her husband. My Grandfathers(A) one of the son (ie my uncle) has no children & is expired (he was married but his wife is not in our touch). Another son of my gransfather(A) (ie my father) is alos expired leaving behind my Mother & Three children (including me , my brother , my sister). Now theres a problem. We (my Mother & Three children (including me , my brother , my sister)) are looking after all the property , cultivating ( cashew planattion) for the past 25 years. We want to get a sucession certificate in my mothers name. We havnt discussed this with our aunt ( ie daughters of my grandfather A) as we are sure that they will not cooperate. its not that they are demanding money but they just want to keep us in a fix. But the major problem is arising as we are not able to apply for demarcation of property of our grandfather(A) to the DC since we dont have a sucession deed. Questions 1. What is the share of our mother & the dayghters as per law in the land property? 2. Is there a way to apply for sucession certificate without informong the daughters of our grandfather? 3. Is theere any other way than sucession for demarcation of property?