signing noc to probate the will

my grandmother died 4 years back, with 2 sons my father and uncle. As per my father who is now demanding me to sign a NOC to probate the will between my father,uncle & elder brother.We are 3 brother and my uncle has a son.As per law do i get a share from my grandparents and do i sign the NOC? if i sign the NOC do i get any share of the ancestrial property? I need legal guidance.