Cancellation of Sale deed

Immovable property (Agriculture land) is situated in Maharashtra. Seller 'A' (original owner) made an agreement to Sell (registered) with 'B,C & D' (first purchaser) in year 2008 and after full consideration completed conveyance deed (registered) in year 2009. They have not done the further procedure of adding/deleting name on 7/12 extract. In year 2010 both the parties mutually agreed and sold the same land to ‘E’ without cancelling (registering) previous deed; and parties of second sale deed were ‘A’ (original owner) and ‘E’ (second purchaser) in which 'B,C & D' were sighted and signed as witnesses in the sale deed. They completed the procedure of adding/deleting names ‘E & his legal heirs’ on 7/12 extract and accordingly modified records. Subsequently ‘A’ and ‘E’ died, now legal heirs of ‘E’ is intended to sell the said property and I am willing to purchase it. There is no dispute between legal heirs of ‘E’ and 'B,C & D' (first purchaser) over land. 'B,C & D' (first purchaser) are supporting the deal and ready for cancellation deed or giving consent in future Sale deed. If I am deciding to purchase this land; Whether this deal is legal and Sale agreement is void? Whether in this condition cancellation deed can be executed unilaterally (by first purchaser); If not then who will be the parties in cancellation deed? Can I go for sale deed by including the consent of 'B,C & D' (first purchaser)?