Uncle Claims Ownership of Dad's Property After 40-50 Years - What Should I Do?

Hi, sorry it's a very long post My mother is 60year old homemaker(nil income) and father is 68yr old retired govt employee (recieving pension).we are 3 children [2 daughters ( all aged between 30-40yr)]to our parents.All of us are married and earning for our livelihood. We sisters are contributing to parents health insurance and other financial things since we started earning and even after marriage ( as my father is an alcoholic too not looking after the household well).Mother has a property in her name given to her by her father as a gift deed. Father had one house and a plot in his name and some ancestral property. Brother went to abroad for studies in 2018 and came back in 2020. He had a girlfriend since his college days( he married to her in 2022, never had objection from anyone of family members ). Since his arrival, he and his girlfriend started involving in all financial matters of my maternal house to the extent he was using my father's debit card for his own use( father says he has given card to brother willfully). Brother wanted to construct a commercial building in my mother's property. He and my father started threatening my mother to register her property ( actually located near Brother's girlfriend house) in name of brother saying if she doesn't agree ,they won't marry off my sister( who got married in 2022 in the presence of grandparents, mother and myself and both my father and brother didn't attend the marriage). They even extracted money from mother's account (which was given now and then to her by me and my sister).During all these process even brother's girlfriend ( wanted a source of income by renting my parents house)also started abusing my mother and involved in all financial matters ( that freedom was given to her by father and brother as my mother was suppressed and we sisters were not aware of things going on). Everything led to the abandonment of my mother who stayed in her friend's place then I brought her to my house. Now after 3 years ( during the course our wellwishers tried counselling and mediation between my father, brother and mother without sisters which didn't work out). my brother got my parents house( and a plot which was in my father's name) registered to his name as a gift deed from my father without informing mother. All the documents of the property gift deeded to my mother by her father is with my brother and father. They are threatening my mother if she enters her own property. Now my mother has no place and income though she had contributed extensively to upliftment of the family all over these years. She ran a grocery store for 15years during which one plot was bought and house was built in that. Another plot was bought after my parents marriage with the help of dowry money given to my father ) but all the properties were registered in my father's name. She has her contribution financially, emotionally and physically. Now doesn't my mother has right to ask back the house and the property given to my brother without her knowledge and to ask for maintenance from my father and also sue all three of them for mental and physical torture..? We sisters want her to lead a peaceful life in her final years of her life.. please guide us.