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