Problem

I am adopted son to my parents. My biological father is elder brother of my adopted father. Somehow my biological father managed to get one-fourth of a land (which was inherited by my adopted father from my grand father) located in our village, through a gift deed (witnessed by me). With the financial support of my younger brother (third son to my biological father), biological father started constructing a house (in the part, which he got from his brother). Patta has not been transferred in favour of biological father. Few months back my biological father passed away without making any arrangement of partition to the family. My elder brother and younger brother have dispute among themselves. Younger brother, since invested huge amounts demands the property in his favour. Elder brother, because of grudge, demand a share in the half-built house. My biological mother was helpless. Now my younger brother propose to sell the property, whereas my adopted father and myself do not prefer it, since we fear that the buyer could cause any sort of inconvenience to us, the reason being all the four sides belong to my adopted father. Also, we do not like a third party purchasing this house, the place being ancestral property and sentimental. hence, pl advice if the gift deed can be canceled or revoked on any legal grounds.