Can an injunction be placed on a person's will to stop them from changing it due to unexpected death to heir?

I am trying to find out if this is possible because my father just recently ped away unexpectedly and he was going to inherit a good amount of land and farm equipment that has been in our family for over 60 years. Now my aunt who has been out of the picture for sometime has come back into the picture and putting her influence on my grandmother to do things that she normally wouldn't. My siblings and I want to see if there is a way to make sure that the things that our father would have inherited if he hadn't ped away will still be ped onto to us.