Agreement to sell

Dear Sir A residential property is a self acquired property of my grandfather. He made a registered will in which he has mentioned that this property will equally belongs to all his legal heirs i.e. his one son and two daughter. This property is lease hold property and partition has not been done Now two co-onwer as per will made an agreement to sell their 2/3 undivided share in that house. Heading of Agreement is "Agreement to transfer of lease hold rights without possession" where as in content it is mentioned that seller will give possession of 2/3 share in this property. Can we give the possession of 2/3 undivided share in said property. As per agreement last date of execution was 02.01.19 but one co-owner has extended it to 12.01.19. Buyer has also given some money on 20.01.19. There was forfeit of token money clause in this agreement if payment was not done by 02.01.19 Now please also clear that can one co-owner withdraw himself from this deal