Gift deed fradulent

My dad bought a property in my mother's name and ran a business in it. My father's legal heirs are three sons and two daughters. Me and my two brother were working with my father from childhood to run his business and developed it. My two sister's were married and father bought a property for them separately in their name. Recently when my father died situation changed and one of my sister used this situation to manipulate my mother. She asked my mother to help her get a loan and took her to registrar office and got her sign. My sister cheated my mother and got a gift deed written in her favor. She have got the gift deed of the entire property which is the source of living for 3 families and my mother. I have worked all my life for this business and now she have the documents in her favor. But she still have not claimed the property. The property is still in my possession and I'm running the business and sharing the income with my brothers. Its the property which should go to all 5 members of the family. But now only one person have claimed it. What kind of suit can I can file against her to get my share in the property. Please give suggestion !