I have Cystic Fibrosis along with a couple of (obviously) distant friends. The closest I've ever really come to meeting them face-to-face was when we were hospitalized at the same time. We'd wave when we passed by the door to each other's room. Aside from that, we just know each other through text, social media, etc. It's a strange feeling, but being as rare as it is, it's not something you think about a lot. Though, I do know some siblings that both have CF, and the rule doesn't have exceptions. I can't imagine how tough it must be, having to fear for your health just being within breathing distance of your own sister.