Should sons file a case against mother for property renovation?

Our family consists of four members (three sons and one daughter). Our father passed away five years ago. Our mother owns a house and commercial land, but our father spent all his savings on the property. The youngest son has been renovating all properties, including the ones under our mother’s name, without the consent of the other children. The mother agrees to all the requests made by the youngest son. He claims to have spent around 3 crores. The daughter does not wish to file a case but wants her share of the property. There was no will written by our father. Should the sons file a case against the mother? Should we accept the 3 crores spent by the youngest son despite the lack of approval? Should we stop the renovations on the properties, and do we have the right to file a case against the youngest son?