Somewhere along the line, the guy's doctor decided that "his expert opinion" is more important than the guy's Right to make decisions about his own healthcare. And then the courts stepped in it too.
If you are not in a position to make decisions about your treatment (and you haven't made a deposition allowing someone else to take such decisions for you) technically no family member can do it.
If the family disagree with the medics? A court has to decide in the best interests of the patient. They are unlikely to overrule medical judgements.