Jagger and Luna are the Maxwell twins, while they also have a younger brother, Valentine. They are from Romania, like the Sterling's.
Jagger was born a vampire into a vampire family, while Luna was born a human. She had to endure the world of sunlight while her brother lived with her family in the darkness.
When Luna came of age, she was supposed to be bitten and turned by Alexander, as a promise the parents made many years before.
Luna and Alexander were supposed to go through the covenant ceremony, binding the two together forever.
But Alexander stood her up and left her human. Then, after Alexander fled to Dullsville, Jagger followed Alexander, looking for revenge.
The Maxwell twins are very similar. Jagger has blonde/white hair tipped with red that falls just to cover his ears, one bright blue eye and one piercing green. Luna has blonde/white hair tipped in red that falls to her mid-back, while most people think her eyes match her brothers, she has bright blue eyes.