Ancestral property

My widowed grandmother has 3 sons. Of which 2 (eldest and youngest)are married with children and the third(middle) is a religious Christian priest. The property is an agricultural land and is in the name of my grandmother. The eldest son is in possession of the land documents and other property receipts and electricity card. A portion of the land is let out on lease/rent for a dealer to park his cars. My query is 1. Is this ancestral property? If so, how can the property be divided. What is the percentage of share the grandmother,her children and 4 grandchildren get? 2. Can the property be divided among the 4 grandchildren (2male and 2female) only? What is the procedure? 3. The rent proceeds are enjoyed by the eldest son and their family only. My grandmother is 85yrs old and is uneducated. She does not get any share of rent. How can the rent be divided among 2 sons and grandchildren? 4. My paternal uncle (eldest son) has taken my grandmother to his house and not allowing her to stay in that land. I fear that he could manipulate the records since she is illiterate and after her death, state that no one else has right over the property except him. Pls advice.