i think you are asking, "what if my parents want to care for me but my spouse wants me to die?"
the form can be modified in any way, according to the instructions. perhaps you could indicate that you require that your parents and your spouse must all agree on any procedures for you, and that absent such agreement, you wish to be placed in the care of any of them who wants you to live.
If my wife hits me in the head with a rolling pin (a distinct possiblility considering my behavior over the years), and I am in a coma, why would I want my wife to decide my fate?