Legal notice

Hello, My question is that Their is a property and my father and father were absolute owners to the property. My father died and my wants to sell the property. We are two siblings and legal heirs to property, but not absolute owners. She did an agreement with a buyer after which she asked me to give a GPA. . I provided her the special power of attorney for sale deed registration before sub registrar. Now the problem is below: My mother took some 20 percent amount while doing the agreement. The property is yet not sold as the buyers loan was rejected. Its been a year , that he was promising to buy the property. They met again to make a new agreement and close the sale deed. But the buyer insisted to add a clause to the new agreement that if the sale deed did not happen in 30 days he will get the full refund back. No one signed the agreement. Now he sent a legal notice to my mother for claiming his money. He also sent the legal notice to all heirs. My question is can he send a legal notice to legal heirs when they are not absolute owners of property. As he has already done.. What is the response i should give ? Is there a way to ask him to recall this notice.