Property will and noc from sister

Hi, We had a house on my grand father name. My grand father and grand mother died in 1990.My father also died in 2008 and the property still on my grand father's name...after death of my father, all legal heirs like me, younger brother, younger sister made a reliqushment deed in the favour of my mother in 2009. My mother then sold the house in 2016 and buy new house on her name. Now she is old and want to make a will on my and my younger brother name. My question is whether the NOC from my sister is still needed if my mother make the will???We are hindu....