Mother's all 3 sisters & her brother's widow wife claiming money

My mother's father has died before his retirement and after his death my mother has taken his govt job and after that she has taken care of her family and her mother. after her marriage she has given financial support to her 3 younger sisters and 2 brothers ( they all are married and well settle). But few years back one brother has died and now all 3 sisters along with their mother came and said "my mother has to give money to all 3 sisters Rs. 100,000 and give money to their brother's son". My Question is i) "is there any provision or law to tell them that if all 3 sisters are well settle, then their is no chance to give money to them". my mother is giving monthly allowance to her mother and we are bearing all the medical and financial support needed for my grand mother. but it is just unfair that giving money my aunties for no reason. Please give me some proper advise for the same.