Legality of Gift Deed of an undivided property

Mrs. X (a Hindu widow) died in the year 1980 leaving behind her three sons A, B, C and one daughter D. The middle brother B died in the year 2015 leaving behind his widow and one son. In the year 2019, D made a registered gift deed of her undivided portion of the residential property (one story building on 1800 sq.ft. land) in favor of C without obtaining consent from A and family members of C. In the month of May 2021, A and C both died leaving behind their widows and sons. So among all the children of X only D is alive now. The property is not divided yet and as per Govt. record the owner of the land is still X. I want to purchase the entire property. All the family members are ready to help me if any alteration is required to make the land legally saleable. Please help 1. Whether the gift deed is legally valid. 2. Is it safe to buy the property ? (Whether the property is free from any present or future legal complications) 3. After few years if I want sell the property to anybody else, will I face any legal complications ?