If ancestral property is gifted to son by father ,

If they/other brothers sign relinqueshment deed in favor one son who has been giftd property by the father in ancestral  property giftdeed is valild.

How is that the property is ancestral?

Pls respond to the point raised by Mr. P.Venu.

If the grandfather was 1st owner of the property in the family chain then it may not necessarily be ancestral.

Until or unless it is thrown into ancestral pool by owner.

Therefore apparently there seems to be no defect in gift deed.

The gift is complete the gift is accepted by donor and confers title with immediate effect.

Moreover other sons have signed as witness.

It might be sheer wastage of time and money to agitate now and it may spoil the relationship as well. 

The property transferred by father to his one son by way of registered gift deed is very much valid and not questionable by anyone, neither his other sons can claim a share in that property as a right.

This property becomes the father's own and absolute property even though he inherited it from his father as his share, hence it is not ancestral property to the children of the father, therefor nobody has any right in it.