Sibella is Lily's little sister.
They share similar appearances and aesthetics, their feminine, genial Perky Goth personalities and domestic hobbies are awfully alike, they share a liking for the outdoors and sports, they're both close friends "normies" (Marilyn for Lily; Shaggy, Scooby, and Scrappy for Sibella), and more importantly, they're both Dracula's daughter.
Miss Grimwood is... whatever the Addams Family are.
She seems perfectly ordinary yet is able to consume poisonous foods without falling ill or dying and shares her monstrous students' macabre tastes. Not to mention as a boarding school administrator, she seems to come from money.
