Assuming you do not store, post, or record any information about a living person, is it ethical to use a living person other than yourself or your direct line as a kick-off point to begin research?
The most common examples would probably be identifying a genetic match and researching them to find how you are related or researching a friend or famous person's family history for fun.
I know that once you go back a few generations, those people being researched would be the ancestors of many people, and then it's clearly generally accepted as being okay.
Specifically, is it ethical to start by centering on one living person and researching without their knowledge?