Cancellation of gift deed

My father & mother constructed a one stored(2 rooms+bathroom+Toilet+Dinning room+Kitchen+Common spaces in all sides) building in 2002,they were the co-owners of that said building.In 2012 they gifted the ground floor to my elder brother and gifted the vacant roof to me maintaining common spaces to both of us like main entrance,staircase, ultimate roof of the building common space in all the sides of the property,I made the entire first floor and leaving in that said portion.My parents were leaving in a room using toilets & all facilities in ground floor.In 2020 after death of my father my brother and his wife creating disturbances with abusive languages,threatened my mother(72+ age) to vacate that room & they are not taking any responsibility of her.Now my elder brother transfer his gift deed(2020) to his wife with encroaching common landing of staircase and with some changes of facts of the main gift deed made in 2012.She is furious and local influential party member,both creating measurable life for my mother.Now My mother wants to cancel the gift deed which has been gifted to my elder brother(2012) and subsequent chain gift deed(2020) as well. Is it possible to cancel that gifted deeds? Kindly suggest what my mother can do to prevent her from ousting from her own building portion which were made from her husbands savings and she has sold all her jewelry to made that one stored building. Can I take legal action on them ? Please help me to help my 72+ years mother as she wants to leave her remaining lifespan in her own room using all facilities in ground floor with all memories of my father.