Procedure for execution of Unregistered will and property division

My father expired n left a self acquired property. I,My mother n my sister are class 1 legal heirs.We hv obtained legal heir certificate.He left an unregistered will.In his will he has given a part of the property to his brother n other part in my mothers name.Pls advise if this will is valid..properly signed by witness but unregistered. Pls guide how this will be executed,steps involved to transfer the property between his brother n my mother.Property is in U.P.