Worrying about him won't help whatever is wrong with him. But आप don't need to fake smile either. Ask your parents या even his doctor if there is anything आप can do to help him when he's released from the ICU.
If आप aren't worried या upset don't pretend to be, just don't be mean या in-sensative. Just do whatever आप think is right don't pretend आप feel one way if आप feel another. btw sorry if I sound mean या anything, but why is ur brother in intensive care. (If आप don't want to say आप don't have to, आप could always इनबॉक्स me otherwise if आप don't want everyone to see. Anyway if आप 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.