> Unless one of those people is my cousin Charlene
The GP's statement can be reworded as a kept secret implies at most one living person knows it. Leaked secrets aren't counter-examples to the GP's statement.
Assuming Charlene isn't a murderer or a ghost (i.e. all of her secrets involve one of the parties being dead), she reinforces the GP's implicit point that it's very difficult to keep a conspiracy a secret unless one of the conspirators ensures all of the other conspirators die off shortly after.
The GP's statement can be reworded as a kept secret implies at most one living person knows it. Leaked secrets aren't counter-examples to the GP's statement.
Assuming Charlene isn't a murderer or a ghost (i.e. all of her secrets involve one of the parties being dead), she reinforces the GP's implicit point that it's very difficult to keep a conspiracy a secret unless one of the conspirators ensures all of the other conspirators die off shortly after.