I would say that Eddie and Julia would benefit from a few sessions of therapy of their own. They have a sibling with a disability, specifically a highly hereditary mental illness, and both of them have responded by taking on an inappropriate amount of responsibility for their same-age or near-same-age sibling's well-being.

This is not just bad for Sophia, it's bad for them too, and I don't think LW quite gets it. In fact, I'd be willing to bet good money that until Sophia spoke up about this, LW actively encouraged this sort of thing in the other two kids.