Okay, so are most the pureblood wizarding families related?

And some half-blood wizards. I mean, if Harry Potter is related to Charlus Potter who married into the Black family that would mean he's related to Draco, Neville, Millicent, Ron, Flint, Crabbe and so on. If these people are all related to the people on the Black family tree it would mean that most of the students at Hogwarts are distantly related to each other and that would mean that Harry and Ginny were already related (very distantly) before they got married.