I had a sister who was two years younger than me.
Unfortunately, it was always she who saw me naked when our family doctor came by. I was often sick between the ages of 6 and 13-14.
Our family doctor would come by, and usually the verdict back then was an injection, followed by a nurse coming over the next few days to give me further injections in my completely exposed buttock.
This often happened in the living room or on the sofa, and my sister saw everything happen.
Conversely, I never saw her naked during an examination.
But actually, we weren't really ashamed of being naked in front of each other, since we often bathed together until the age of about 12.
What I do remember is that my sister had to go to the gynecologist for the first time around the age of 17.
I knew this from my mom, because my sister was very embarrassed about it. She didn't want to talk about it at all, but I teased her a bit about that examination.
Then she would get quite angry.