Is an agreement valid without a notary?

There are three brothers in a family like A,B and C. A eldest and C youngest. Govt acquires property in name of B and C which were ancestral property and govt compensates B&C. A, B&C make an agreement on 1000 stamp paper to distribute the compensated amount and all 3 sign the agreement. The agreement does not have witness and is not notarized. After the govt compensated amount is distributed in A,B and C then B files a case in court after seven years that the agreement is fake and wants money back. C has no objection to the distributed money. What will court say in this matter.