If the caregiver is too sick to help your sick parents, I agree that they should be on someone's radar...have you called social services for their county to see what they suggest? How sick are they? If they are getting worse quickly then 911 should be called.
I would get them to the hospital right away! Can you call 911 and tell them the situation, provide their address, and ask that they be taken to the ER for treatment? That would seem the sensible solution in this situation. Not sure what you mean by "too sick to go in the home".....? A nursing home? You might want to expand on your question and provide more details because it's hard to know your intent from just a header.
Regardless, call 911 or whatever the emergency number is for where you live and get them to a hospital.
Good luck!