Property distribution to one son only

Respected sir, My grandfather was died on 2004 and my grandfather have two son and one daughter.after my grandfather death my grandmother take signature of her sons on the document. i don't know the type of document and register all the property to herself. The property is inheritance property. My grandfather acquired that property from his father. Few month ago my grandmother made 'will' document in this her all property equally divide between sons. But currently she made one more will in which she gave all his property to one son only. Tell me the solution. I hope you are understand and give me the best way out regarding this.