i know a family in the same situation, except i know the younger sister (who is my friend). her parents are v. traditional (both extremely smart doctors) and their elder daughter has down syndrome. my friend is also really smart and is studying in med school currently. but she has tremendous amount of stress tp do well from her parents and she was forced to mature v. quickly as her parents assumed the responsibility of taking care of her elder sister will be hers when they pass away..