Families naturally assign roles to their members—the Golden Child, the Scapegoat, the Caretaker, the Rebel, or the Peacekeeper. Drama naturally occurs when a character attempts to break out of their assigned role, upsetting the family ecosystem.
Families are miniature governments. Who holds the power? The eldest son? The financially successful sibling? The emotionally manipulative parent? A great drama storyline constantly upends this balance: a parent ages into dependency, a black sheep becomes the only one who can save the family business, a secret bankrupts the family's moral authority.