Regarding will

Sir My Grand father has 1 daughter n 2 sons. They have written a will and registered .In that will they have written that only 1 son (my father) has only rights on their property remaning 2 heirs have no rights on their property. Can we transfer property by will on the name of my father. Is both heirs require sign in court? as both heirs are not ready .As they have also interest in that property. Sir and what will be the procedure to transfer property and time period? Plz suggest sir.