Rights of Coparcener over ansestoral property

Hello, my grand-father own a agri culture land. my grand father died in 2012. and right now my father have total 4 sisters and 2 brothers. all sisters are married. my grand-mother is with father. my father take care his mother. i want to ask here share of contribution in property as per gov act. since my father have take care his mother and father from beginning. no sister is contributed to take care my grand parents. can they claim share in property? all sisters are married before 1994. it is more than 20 years my father is taking care my grand parents. so please help me and let me know. is it necessary to take any kind of NOC letter from my father's sisters before property distribution between my father and my uncle