Years later, the younger sibling is an adult but still "acts out." The eldest continues to micromanage, unable to stop "parenting." When the actual parent tries to return and seek forgiveness, the siblings are split: the youngest wants the parent they never had, while the eldest refuses to step down from the throne of martyrhood.
Often, the most satisfying arc for a protagonist in a family drama is not fixing the family, but accepting that they cannot change them. Growth looks like setting firm boundaries or choosing to walk away. genie morman incest family 272 hot