Demand in property by step sister's son

My father in 1984,distributed self acquired and ancestral land among we 4 brothers. father died 1991.Now my step sister's son( sister who died in 1985 ) claimed his mother's part in all the property. Father sold some ancestral property for sister but no proof is available. Wheather the grandson claim in self acquired property? What to do for the ancestral property sold for sister as of now we don't have any proof.