Inheritance of Proporty by 1st Class heirs

My father has 2 brothers and 1 sister. My father's sister was promised to be given an equal share in the property left behind by my grandfather after his death in 2011. She was invited to a court where she was made to sign some papers under the pretext that she would be given an equal share in the property after selling it off but since she is not well educated, she was hastily made to sign some documents in the court and after that she never received any share of the property. There were two properties that my grandfather purchased in Delhi during his career, one of them was sold as I mentioned above and the money obtained from it was shared only among my father and his 2 brothers. The second property is now in possession of one of my uncles (brother of my father). I want to know if this unfair distribution of parental property can be challenged in the court in favor of my aunt (sister of my father).