[Dawn]

You should make it clear that if he wants something that is not his, to ask before touching, not only does it give you a clear mind knowing where your item is but if he does take it to a friend's house or sell it, than he is the one liable replacing the item since the item was not his in the first place to sell.

And if he takes an item again without asking, threaten to call the police cause that is stealing and he needs to learn that his actions has consequences. And if he takes from his family, he could be taking from friends or worse, he could form the habit of just taking items from shops! Nip it in the bud before he does something he's not going to be able to easily walk away from..

And if you know what type of items he usually takes, I agree with Choco, either find a spot you can hide it or if worse comes to worse, since I'm not sure if the KH you are preferring to is the Gameboy or PS one, I would invest either in an CD storage wallet or Gameboy cartridge case and place all your loved games in there than put the wallet in your purse or backpack that you keep with you at all times. Only leave the items you don't care about if they go missing, out in the open. Gradually when your brother sees that the items he wants are not easily accessible, he will start requesting permission to borrow or learn to save up and get his own.