Legally, you can not do anything. However, you can involve your parents in the situation to put some pressure on him to return the money back. You can tell him if he will not return the money you will escalate the issue within the family members and even your common friends and hurt his reputation. If he doesn't care about all of this, then your chances are zero to get your money back. Sorry.
"I set up a bank account in South Korea and I put my brother's name towards the account holder."
I think you know that the money is gone and you just paid 40k for a lesson so I really hope you learn from this matter.
Freinds , family and money does not mix well together
Best of luck
Sorry, but legally he had a right to the money. Nothing you can do.
You gave him $40k. He used the money you gave him. Stop hiding your money overseas.