Share of property of my mother in his father property

My Nanji has 4 childrens i:e ( 1 Daughter ( My Mother ) , 3 sons ).

My Nanji expired on 16 July'19 . 

In all my nanji  bank accounts , my mother is not nominee.

Also the house built my nanaji  , does my mother has equal share / right in house porperty .

Can my mother challenge the will of his father if nothing is given to her and all property given to his sons .

Does grand sons & grand daughters has share in grandfather porpoerty