Mother Told My Uncle To Have Her Money Split Upon Death, He's The Only Beneficiary And Refusing To Split

My mother was terminally ill and had told my uncle that he, my brother, and I were to go to the bank with a death certificate to withdraw and split her money. He told us this. There are no notes, she didn't tell us, and she had no will (crazy, I know) A letter was sent to my parent's home notifying us her account was closed, and there were no separate accounts my brother or I have access to. My uncle is saying he was the only one listed, it's his money because that's how my mom had set it up. I'm not sure if there is ANY case that can be made against him to split, as legally I don't think he's obligated to. Any suggestions? (Yes I've reviewed all of my accounts to ensure my family doesn't experience this some day haha)