Fire Blood

The world known as Earth always had been ruled by the Pacem bloodline, the Fire Bloods. They posses the most powerful kind of magic. Pacem, the first Fire Blood and first ruler of the Earth, made a lock to prevent wizards and witches from killing. The rule is: keep the bloodline pure so no one with pure blood wants to break it.
When Cevro, the Fire Blood ruling Earth at that time makes a mistake and gets three children by a non-witch, those three children take over Earth and do everything in their power to break the lock.
But Cevro got another child by a witch. She is Earths only hope to take back her kingdom and keep her people safe.