Ownership of Property

My Grandmother made a Registered will in the favour of her Younger Son Wife in the year 2006 and my Grandmother have three sons in which two son have given Notarized No Objection Certificate(NOC) letter to My Uncle wife that they do not want any property from my grandmother but in the year 2016 My Grandmother made another Registered will for the Same Property in the favour of their three sons. So,I want know that which Will are Valid Now. And their is any problem to the new will after giving the NOC.