How do we deal with our brother who is seeking guardianship over our mother?

Our parents have a revocable trust, listing our brother as having the power of attorney. Our father passed away in 2004 and since then our brother did not communicate our parents' financials to our mother nor the remaining siblings. Our mother changed her revocable trust, removing our brother's power of attorney and listing her three daughters as the co-trustees, attorneys-in-fact. Since that change, our brother sent all three of us daughters a registered letter, stating he no longer wanted to be contacted for any reason. He had not contacted our mother for over 18 months and has now started stopping by and leaving nasty harrassment notes. Since then he had requested a psychological evaluation of our mother, saying she was "coerced" into changing her revocable trust. He also applied for guardianship, which was denied. He now is applying for guardianship again! To save our mother any more legal fees, should we wait and see if he actually does get guardianship? Or should we apply also even though her revocable trust lists us three daughters as her power of attorneys In fact financially and medically?