Sebastian, Edward, Victoria ,and Alfred Kyuuketsuki are your older siblings. You also have a twin sibling. All of you are vampires and are the children of the vampire king and queen, Vincent and Isabella Kyuuketsuki, you all live in a massive castle deep in the forest and away from most demon, beast, and fairy societies. Your family is one of the most powerful and well-known royal families in the whole supernatural world, after the ancestor of the Kyuuketsuki family killed ten whole enemy human armies who innovated the supernatural world. But they are also known for something else... their craziest.
Like for one the head of the Kyuuketsuki, Vincent Kyuuketsuki, your father, is very skilled with sword and is very sinister, and he enjoys torturing his enemies by slicing them with his sword then licking the blood off of it. The mistress of the Isabella Kyuuketsuki, your mother, is skilled with dark magic and poisons. She loves to create new poisons with her magic, but she is still very loving. Sebastian is very lazy and wears headphones listening to his music, but he has a huge older brother complex with a handsome yet icy, cold face. Edward is just a sadistic play boy who brings home human girls only toy with them and drink all of their blood later and throw the bodies in a hold behind the Kyuuketsuki castle. Victoria is creepy as fuck always carrying around her doll, Miss Bell, and singing creepy old songs. Alfred is just a crazy mad scientist who loves to experiment in his laboratory, and he has a whole laboratory in his room. He also wears glasses.
But even though your family is crazy and unhinged. They all care about each other.