Your little brother’s ceiling is often whatever you showed him was possible. Raise it.

Younger siblings do not calibrate on advice. They calibrate on what they have watched somebody in their own house actually do, because that is the only evidence that it is possible for people like them. Whatever you attempted set the height of the bar. He is reading your behaviour much more closely than your opinions.

So let him see one hard thing this month: the audition, the application, the subject everybody says is difficult. Let him see the attempt and the result, whichever way it goes. That is how the number in his head goes up.