Title suit case by younger brother on my father

Property was purchased by my late great grand mother. On time of purchase she was widow. By inheritance property Mutation is done in name of my father . My father sold that property to some one. I don't have any objection in it. But my younger borther filed as title suit civil case on my father, me and the person's who bought it. My brother want 1/3 property and reverse the registration. This is not ancestors property. My father is owner and have sell right the property without any consent.