Family Property Forgery by her own brother

This is a teenage from Virudhunagar, Tamilnadu. We are Hindus. My grandfather (mother's side) has properties in virudhungar. As my grandfather died decades ago (1999), all the property documents are with my grandmother. My grandfather had 3 daughters and 1 son. My mom is 3rd daughter. A few years back without my mom's permission they got PATTA for all the property documents in his only son's name. As my mom did not know about it at that time. However, almost 3 years before my mom got a call from a PATTA office, asking that are you ok with getting PATTA for the property in her brother's name. This was asked by a government official at the PATTA office. She immediately denied approval. Then they weren't able to get the PATTA for that property. For all other properties, they have used some other persons on behalf of my mom and got approval for getting the PATTA. My mom needed, what she deserved to get according to our Indian law. Kindly advise us on how to proceed.