I do feel bad for your Mother, that's a lot for her to have to deal with. The good news is she can go completely no contact with them if she chooses to do so, or very low contact.
She can protect her assets through legal means.
I understand there is probably a lot of water under the bridge for you with your siblings and you resent them appearing now in what seems to be a very disingenuous way. Sorry you are having to deal with that too.