What are my options in getting guardian of the estate for my Dad?

Long long road. My brothers have stole and manipulated their way for years. My parents are now old, one has late stage Alzheimer's disease. Youngest brother manipulated to get hold of her social security money, but her needs and expenses fell on me. He doesn't work. None (4 of 5 of them) don't work. They 'stay' at my parents house for 15 years! Lived off my mom and dad, till mom got sick, and they had the nerve to report me to the state saying I was committing elder abuse. The state granted me guardianship over mom anyway!

Fast forward, my dad is now in trouble. He's a harder situation; he regards my brothers way more than he does me. Although I have always helped him financially. For 10 months he complained that his bank account was manipulated. I had time to check it 10 months later (I didnt want to help him due to our strained relationship) and found out he had all kinds of stuff done to his account. I absolutely know my brothers took full advantage of his account. I contested the fraudulent activities. he received all of his money back, JUST to turn around and have my brother take him to another bank, open a new account and he gets my dad to sign power of attorney paperwork. I had my dad sign POA for me a week before, but the bank rejected it, saying they already had one on file. The bank manager was a Big (or really little :-) DICK! He prides himself on being a protector of the seniors at 'His' bank, yet he's like there is really nothing he can do about the situation, when he is full aware of my dad's incompetency and what has happened with my dad and how my brother is manipulating.

Sadly, I feel manipulated. I did not report my brothers. They opened up credit cards in my name, my late stage Alzheimer's mom's name, and likely my dad's name, and I know they were the ones who took money out of his account. Even more pathetic, I believe if I were to report them, my dad will be lost without them and be mad at me for reporting.

I do not know how to get him to court and get guardianship. It just happened that way with my mom, The Corporation for Aging was involved with her care so that was easy. My dad is not associated with any senior services.

Please help!