Why not tell the brother few things to make him more cautious?
She can at least warn him about one thing: to never give the Aurastone to the magic tower, no matter what happens. Even if Jaina asks.
Though if the brother is stupid he will still do it anyway.
![nyoron :nyoron: :nyoron:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)