Dana Vikrayam---Gifted land

When my son was going for studies abroad, I requested my father for my share of property. Though he was willing to give my share, my brother with whom my father was living in the village refused to part. Then my father gifted to my son 25 acres of dry land as "Dana Vikrayam" All this happened in 1990. After that there was a big quarrel with my brother and father. Since he had to live in the village, I and my son were forced to write on the deed that we do not want this land and signed and gave back the deed papers to my father and that was not registered. My father expired in 1995. Then my brother was cultivating the land for himself since I was in job out side and rest 2 other brothers in USA..My brother too expired in 2013. Now his son is refusing to part with the gifted land nor is he willing to give my 1/4 share. I took a copy of the deed from Registrar and found the title of the gifted land was In my son's name.My brother's son wants tofile suit.. What is the law about this please?