Gift deed by Brother to sisters

Hi , My mother brother transferred ownership of property through gift deed to his sisters (including My mother) on 2015.This property acquired by my mother brother through family partition in 2005. In the gift deed he mention , while family partition took place in 2004/2005 there was no allocation property done to daughters of hence considering the point he transferred the property to daughters in 2015.In the gift deed, my uncle had mentioned he is the owner of property and no body from his family member will have the any rights on property. Except this property still other properties are acquired through family partition and currently he hold the ownership of other property However, while creating gift deed, My father -in law (Sister brother ) had not taken signature of his major son and sister. Now in (2020) his son has filed case to cancel the gift deed since there was no consent from both the Childers of my father in-law. Would like to know , What is the law around this situation and does his son has the legal right on property which is registered based on gift deed. Thanks