Mom won't say who she named power of attorney?

How long ago were they prepared? Maybe mom does not remember what she did. If she is competent get her to her attorney to review. She may want to change something.

In this state the persons assigned POA don't have to sign anything.

It would be pretty pointless to have a POA and not tell that person! You don't have to tell other family members (though why not?) but how can the POA duties be handled by someone who doesn't know they have that role? !

It would be a simple matter for mother to set up a new POA, rescinding any she might have forgotten!

What, specifically, are you wanting to do now that would require you (or someone) to have POA? Or are you concerned about the future? Maybe Mom is right and she has everything set up the way she wants it with the lawyer.

We were never asked to sign anything. She said she thinks it's my brother but isn't sure and won't let us speak to her lawyer. She just keeps saying 'don't worry, everything will be ok'. I'm ready to strangle her. She doesn't give a d@mn how much stress this is causing her children.

Second thought all states may not be the same.. I'm in MA.

I just looked at my Mom's POA and I had to sign it agreeing that I understood my responsibilities...

So I assume if it was you or brother you would have remembered signing..

You might have to petition the courts to get guardianship of her. Unless there is someone she trusts that can talk her into telling you if you or your brother has POA. Or can look around the house for the documents.