Boyfriend stole from my brother.?

So my boyfriend stole an ipod from my brother and I found out because I saw it in my boyfriends bedroom. Then I asked him about it and he said he was just borrowing it and then we discussed everything. I forgave him and everything but I'm worried it will happen again. I don't trust him by himself in my room or any room in my house. What should I do? Thank you very much!