My dad is 85 with Parkinsons and some dementia (or maybe it's the medication side effects or maybe it's lifelong mental health issues). He's definitely in stage 5. His younger brother, who he loved like no one else, just had a massive stroke and is unconscious. He will be devastated when he finds out. I'm actually scared he'll have a heart attack (he's already had one). So for some reason, my mom, sister and I haven't told him. He has a good memory. And people visit him. So we have to tell him something at some point. What do we say? His brother is not concious, although that could change.
I wouldn't say anything for just a few days now. If he comes out of the coma then it would be "Dad, your beloved bro has had a stroke. He's in hospital and getting the best of care, but this is going to take some time and some rehab and PT work. We are sending your love to him. What should we tell him?" Make it as hopeful as you can.
If the coma continues try to say nothing cannot last long. You would then have to go with, as tho it just happened "Dad, brother has had a stroke and he is in a medical induced coma to rest his brain. We won't know anything for a while. We are supporting his family and will let you know, but he is comfortable and resting. This is a wait and see for us all".
If he's gone, then it is the "stoke and he is gone; no pain and was peaceful. Know how this hurts you."
I wouldn't outright lie, but I would fudge this the best you can. Your Dad is 85. If he has had a stroke and he has Parkinson's then he has outlived many many with less. If honesty and the very sad passing or illness of his beloved bro DOES take him, then you will know there wasn't anything to be done. If you are a person of faith then they would be together. If you are not, then they are at peace?
I am so sorry. Just so sorry. My brother was the Hansel to my Gretel in every dark woods of life. If the grief of his loss didn't take me right on out after him I can only believe that grief doesn't kill us. We have all heard anecdotal evidence that it MAY. But I think that no reason to lie to people we love in the end.
If his condition doesn't improve and you can't trust that a visiting family member will keep it quiet, you probably have to tell him. Is there any way to stall that until it becomes clearer if the brother will improve? Seems like it would be much easier if his brother were on the mend already by the time you tell him.
See how he takes that information.
If he handles it well then tomorrow get an "update" and then give him more information.
If he has a good memory and people visit him he will eventually find out what is going on.