MOU VALIDITY AND BINDING BY HEIRS

Sir..father entered into MOU to agree to sell a property at 5%of market rate after its court dispute case is settled in future. He also recieved each month certain amount from the purchaser. Court case is still pending and father passed away. Purchaser stopped paying each month thereafter. In MOU father is stated as Vendor ( which expression shall unless it be repugnant to the context or meaning thereof be deemed to mean and include his heirs, executors). Is the MOU still binding on my mother or we children. We want to revoke this MOU.Or even cancel this and go with anyone giving better deal. Under what clauses the existing MOU can be cancelled. Request help.