Have you ever had chickenpox?
Hi Researcher. I'm sorry to read about your brother and wish him well. Welcome to this site and feel free to make yourself at home and ask questions.
But first, in answer to your question about chickenpox, I did a quick google search and came up with this information:
Chickenpox is a highly infectious disease, usually associated with childhood. By adulthood, more than 95 percent of Americans have had chickenpox.http://www.chw.org/display/PPF/DocID/22739/router.asp
And yes, I'm one of the 95% who had chicken pox as a child.