I don't disbelieve you and that sounds awful and life-changing, but there is a difference between "this awful thing could happen to you" and "this awful thing will happen to you", but the brain cannot easily see that difference so stories like this tend to make people feel a lot worse than they have to. The truth is your bro is uniquely and tragically unluckly, but any given young person has a very low probability of experiencing serious adverse effects compared to someone in a risk-group.

It may seem like a callous thing to say, and I wouldn't post it anywhere else because I wouldn't want to feed virus skepticism by echoing the "its just a flu" people, but that isn't a problem here so I can be honest and I honestly think it is more callous to say "I can't believe old people get the vaccine first", sorry. If you are young you kinda have to just suck it up because this virus isn't really dangerous to healthy young people anywhere near what it is for unhealthy or older people and that is just a fact, your bro's unfortunate circumstances aside.