I doubt that Togashi learned about pop psychology before starting Hunter X Hunter so it's crazy how each of the Zoldyck siblings fit perfectly into the roles assigned to children born into a narcissistic family.
Illumi and Milluki are the flying monkeys of their parents who see it as a duty to control and abuse their younger siblings.
Killua is the golden child who is seen as the perfect heir by his parents and crushed under their expectations.
Alluka is the scapegoat who was dehumanized and locked up.
Kalluto is the lost child, quiet and forgotten by everyone.
