So you are essentially shouldering some/all of the responsibility for the brother's alcoholism upon the OP. That's a big burden to carry, and potentially dangerous + damaging if it is not true.

You're taking a wild guess with that comment, you have no idea, and (maybe unintentionally) your sentence doesn't ask if that could be the answer - you state it as the case (the words 'if' or 'maybe' would have been better here).

When people are looking for answers they can read into the linguistics of things very carefully. What you wrote was very powerful and without any facts or evidence to back it up.

I would be sad if the OP, who already clearly feels worried about the situation, started taking responsibility for this mess that actually wasn't his doing or responsibility.

I'd be even more sad if he gave up his startup and moved home when it turns out none of the trigger factors for the brothers alcoholism have anything to do with him. Many people just self-destruct and even if the alcoholic brother is missing his distant brother that doesn't make it wrong for distant brother to live abroad.