Firslty, Sir, as you have explained that your mother has a share in the anscestral property of her which means that now you have right over her share in the property.
Secondly, you and your sibling if any would get the share out of it.
Thirdly, you should fisrt apply for the succession certificate in the civil court to claim your rights over the property.
Fourthly, then you should file suit for share in the property share of your mother being the legal heir of her.