Legal heir issue

Hello all, ' Is it possible to add names in legal heir certificate which is already been issued? Actually my brother passed away in 2015. We didnt apply for a legal heir since whole was living together without any issues. But the property we live in was my grand father's, they passed it to my mother and my mother passed it to my brother for business purposes. But his wife applied a legal heir certificate without our knowledge. In that only she and my mom's name has been listed. I have two married sister's. If not mine atleast can we add the sister's name in legal heir certificate.