My grandfather daughter name nagamalli and son name thiyagarajan, Thiyagarajan son Surya
My grandfather gave dhanam settlement to his daughter nagamalli ( my mother) for 1.29 acres on 24/05/2017. Later he gave 'will power' all his property 3 acres ( that 1.29 acre included) to his daughter nagamalli at register office on 25/09/2017 and grandpa died on 31/10/2017
Grandpa son (Thiyagarajan, who is nagamalli Brother) got signature from grandpa on empty document before 2 days grandpa died
thiyagarajan used that empty document signature as grandpa giving will to his Thiyagarajan son Surya using rotary lawyer and did forgery( this forgetation date given as 04/08/2017)
I want to know that forgery 'will power' document becomes legal?