The policies I’ve seen cover the sick person and any travel companions. In our case, we’re all in the same family. I’m not sure if that matters, though. Here’s what it says on the Travelex site:

“If you or a traveling companion contract coronavirus while traveling, and it is diagnosed by a physician, you could be eligible for trip interruption, trip delay, emergency medical and medical evacuation coverage.”

The mandatory island insurance does only cover the sick person, so it’s one more reason to get something additional.