Can granddaughters have equal share in grandfather property?

My mother is the only child to my grandfather, my father didn't had any wealth so he stayed in my mother's home and looked after their property. But my brother made a will as though my grandfather made it stating that whole property belongs to him and took my grandfather's signature. This is not the self earned property by my grandfather instead this is passed on from his family generations. The will was made in 1996 and my grandfather expired in 1998(20 years been over since the will made). my father expired in 2008. my mother is still alive and she is on our side saying that we daughters too should have equal share in it. can a case be filed against it with my mother on my side?