How do I help a ill family member with health and financial decisions and they don’t want to sign a healthcare directive or power of attorney.

Unmarried brother , age 73, lives alone, has been showing signs of mental impairment for over a year. The past 3 months have become increasingly worse. Recent hospitalization for diabetes, acute liver injury and enlarged prostate has left him weak and in need of intervention. Brother has refused to sign healthcare directive or power of attorney. Claims he wants to be “free” and make his own decisions. Patient privacy laws has prevented me from communicating effectively with doctor. Recently told me he drew money out of his bank account and deposited it to his girlfriends granddaughters bank account. A red flag went up. How do I protect my brother, to act on his behalf and protect his assets.?