Calypso Monroe, a siren demon, and Samara Monroe, a succubus, are famous singers. They're also adoptive siblings, they were left at an Orphanage when they were babies. They met when they were 10 and soon became best friends, they both got adopted together by an Imp couple and they began their singing career. They're both 16, in high school, and on their birthday they are sent a letter from a member of their birth families.