Why shouldn't the government lock up a criminal that does so much damage? And what does it have to do with you? Does it matter that he is your brother? Are we supposed to judge you by his actions? Are you saying we are lucky to have a benevolent dictator such as yourself?
.1 If my brother and I were one person, it would go from illegal to legal but nobody's balance sheets would change.
.2A (use this one if you like historical materialism) Laws and ethical notions are constructed because of balance sheets. Why, then, don't we change the law so that the apparently arbitrary distinction goes away?
.2B (use this one if you like utilitarianism) There's no basis for law beyond utility, and it's obvious that both cases have the same result. Therefore, there's no basis for a legal distinction.
I've never figured how to get out of this argument, except by making private property a fundamental right. That sounds a lot like objectivism, though.
You may not know this, but I am the richest man in the world. All economic activity is technically mine, carried out by stewards of my capital. However, I have decided that the most humanitarian approach to this massive responsibility is to let things run their course - I am comfortable on a meager living, so I take no interest. It's not like someone is going to replace me: after all, everyone in the world simply manages my funds, and does their best to earn the right to manage more.
Now, my brother on the other hand - he's a notorious criminal. He owns nothing rightfully, but his famous heists have resulted in a 3% annual decrease in the value of every bank account in the world; and even worse, the multitude of shots fired in the ensuing high-speed chases have done the same to essentially every asset.
Congress has decided to close the loopholes my brother has been using to escape justice, but they're fine with me.