Can papers of property sold by mother be modified after her demise

Can a property which was sold by my mother 15years back be rectified now by me after her demise . 15years back , my parents had sold their property to a purchaser. our actual plot was 30*40. since, my parents were in good terms with neighbours and we lived in brotherhood as they had already constructed their house,30yrs back and had helped us in many ways. we left that portion to neighbours although we didnt make an agreement and but we registered 36*30 size to the party and sold them for so much worth only. Now after 15years, after my parents death, that buyer has come to me and asked me to rectify the document to 30*40 in order to break the house of the neighbour. Is it legal to do so. Can this be rectified after 15years , after death of my parents from my end to a buyer to whom my parents sold 15years back.