Property Registration

Good After noon madam/ sir 2 years before we had planned to bought a house. It was placed nearest to my house. The total amount of the house was 17 lakh. We paid 2 lakh as an advance. We told the seller remaining amount will be paid at the time of registration. The seller and him mom put a sign on 20rs stamp paper. After 2 months they asked money we gave 5 lakh, as per the continuous request we gave 3 lakh, they put a sign on 20rs stamp paper. totally we gave 10 lakh. venkatraman is the owner of this house. He passed away. he have 2daughters and 1 son, one of the daughter was passed away, 1 son and 1doughter, and her mom is ready for the registration. the passed away daughter have one son, that grand son is not willing to this registration. they had no death certificates, heir certificates, now they delayed for the registration , please give a solution how we can solve the problem. Is their any possibility to claim amount from them. other wise how long it will take to registration.