How do I prove fraud?

My brother gifted my father's entire fortune to himself and hid it under his wife's name and investments. My brother failed to communicate to me that he stripped me of my medical power of attorney cause i knew my dad wanted to be buried, and he objected cause of price. so he went against his wishes, and cremated him. Problem is: he became Power of attorney financially, and wasted no time to gift it to himself. My mother is a widower now, and my dad wanted her to have the rest of his money. My brother did no sudh thing, and i believe him and my mother struck up an agreement concerving some of the money for his four kids. He recently became a realtor, but was doing so well with his senior mortgage position at remax. i do believe he obtained a small fortune, ripped off the nursing home by hiding it, and walked away with the attitude only explained in a narcissistic manner. Please, what steps can I take to uncover this criminal behavior. I don't even want money, but he upset me so much when I found out about his wife on medical power of attorney, which I did not know until I called my dad at his home and my brother stripped him of a phone and instructed the staff that only he or lauren could talk to my dad. I learned of his death via textmessage. Morally devoid is my brother.