A million dollars is not a small amount of money to just “forget about.” Your brother is basically stealing from you at this point and hiding behind family loyalty to get away with it. Family or not, you wouldn’t let a stranger take a million dollars from you, so why are you letting your brother do it?
You need to get a lawyer immediately. I know that sounds horrible because it’s your brother and nobody wants to sue family. But he’s the one who made it business when he took your money and refused to give it back. If there was a written agreement or even text messages about the loan, you have a really strong case.
Start by sending a formal demand letter through a lawyer. Sometimes just seeing that you’re serious and willing to take legal action is enough to make someone suddenly find the money. If he still refuses, then you actually have to sue him. I know it’s ugly but a million dollars can change your whole life. You could buy a house, invest, start a business. You can’t just walk away from that.
Also, think about what this says about your relationship with your brother going forward. Even if he eventually pays you back, can you ever trust him again? Probably not. So you might be losing a brother either way. At least get your money first so you don’t lose both.