Mothers property

Dear sir, My mother expired due to ill health in 1979.she made a registered will making my father as guardian of property inherited by her as i was minor.she wrote in the will keeping faith on my father to look after me and the properties.My father hide all the facts about the will and sold part of my mothers property to others.How can he sell as he is not legal heir.he was only the guardian.Can i file case on the party who purchased the property.Recently i came to know about the facts.only small portion of the property is left.we are three brothers who were minors during my mothers death.thanking you shaik khaza mohiddin.