Let the boy do whatever he wants with his life, even if it is the most stupid, horrendous mistake. He will then be able to be proud of all the years he has completely wasted, all the money he has never earned and all the pension that he doesn't have.
Do everything you can to save your brother from himself and his youthful, misguided and idiotic choices.
Never judge a man until you walked a mile in his shoes, by then it won't matter, you'll be a mile away and you'll have his shoes.