In the US, does a parent have any heightened duty of care to a grown child than that of an adult stranger to another adult?
Financial aid programs presume a parental contribution and will deny any aid to students whose parents don't cooperate in the process unless they qualify as "independent" (e.g. if they are married).
A parent generally has an obligation to support an adult child who suffers from a disability that prevents them from functioning.
But, generally speaking, parents have few legal obligations to their adult children.