Worrying about him won't help whatever is wrong with him. But tu don't need to fake smile either. Ask your parents o even his doctor if there is anything tu can do to help him when he's released from the ICU.
If tu aren't worried o upset don't pretend to be, just don't be mean o in-sensative. Just do whatever tu think is right don't pretend tu feel one way if tu feel another. btw sorry if I sound mean o anything, but why is ur brother in intensive care. (If tu don't want to say tu don't have to, tu could always bandeja de entrada me otherwise if tu don't want everyone to see. Anyway if tu can't say I'd understand)
Be realistic about it, but not too realistic. Be as optimistic as u can about it. Having an optimistic attitude will help u be happier,and there's still hope for him. And also, if u feel like crying, then cry. U sometimes just need to let it out. :) I hope this helps.