Validity of gift deed executed

Sir, My grandfather and his two brothers had separated their joint family properties and executed partition deed in the year 1935, by then they lived independently. After 1935 my grandfather independently purchased some properties with his personal income earned by business, we have much documentary evidence for the same. All the properties which he purchased after 1935 sold independently by himself since 1944 to 1982 except three items, out of that two items without my grandfather knowledge his elder brother executed Gift Deed in favour of his daughter and son-in-law on 1986 mentioning wrongly that he has 1/3 share in said two items, another item he has not claimed the entire land in said two items enjoying and possessing by my grandfather and us only since 1938 by paying land revenue tax to Govt. under our personal Patta, still gift items our names are continuing in revenue records since 1938. The donor and his sons not mentioned said gift items in their regd. partition on 1955 where they admitted partition among my grandfather and his brothers took place in the 1935. Donor did not claimed gift lands filed before land ceiling tribunals. Donees and Donor never in possession at any time. After demise of my grandfather in 1987, the legal heir of my grandfather got (regd) partitioned including said gift items in 1989. My grandfather and my father mortgaged (regd) entire land in said gift items on 1969 to Ag. Bank. The legal heirs of deceased donees filed suit for declaration of title and right on 2005 in the trail court of A.P. against us, trial going on. Kindly suggest your valuable suggestions with latest Supreme Court judgments regards