9. Superman’s Cousin
Supergirl isn’t just a female version of Superman…she’s his cousin! In fact, Kara would often babysit the baby Kal-El back on Krypton, so when she arrives on Earth and meets the now adult Clark Kent, her reaction is obviously one of shock (the reason for the age difference is that the ship she was sent in was delayed in reaching Earth).
The big question of course is whether or not the Man of Steel will play a role in this series or if Supergirl will exist in a world where Superman doesn’t. Another option is that they shake things up so that the two do arrive on Earth at the same time, and that would make sense. As a result, Clark would only be roughly ten years of age, freeing the series from the burden of touching on Superman’s existence.