So recently me and my wife have taken in her nephew to live with us for a while, as he has issues with his dad and doesn't want to live there. He's lived with us for 2 months so far We have been together for 6 years, we don't have any kids of our own but we treat him as our own because we love him and he loves being here. He's 15, I'm 42. He knows no boundaries and always comes into our bedroom when we're not there, and takes anything he feels like borrowing up to his room. He's taken my ps5 pad up because 'his had run out of battery', he's taken my wife's hairdryer up, and today I noticed he took my sleep mask upstairs (I work nights) and it had run out of battery. I live on a noisy street and I use my sleep mask for noise reduction. My wife thinks I should just let it go, and it's small stuff which doesn't really matter. But i think the kid needs to know boundaries and not come into the room without asking, and definitely not take things without asking. Am I the asshole?