Senior citizens.. important question on medical proxy. I have no one to turn to..?

but you, dear answerers who are always so full of wisdom. Having a very small family (and my friends are worse off than I am so I cannot depend on them as their health is fragile and they may not even be here at the time this arises) I HAVE NO ONE absolutely no one, I trust to be my medical proxy and carry out my wishes if the need arises. The only one I would have considered is OUT. They have TOTALLY different views on what should happen with a person who is incapacitated. THEIR views come first. THEY do not agree with my wishes, and have blatantly told me so. Their views would come first. SO I cannot name them as a medical proxy. My question: what does one do to make sure their wishes should they become incapable of making these decisions, are TRULY respected and carried out? ps, I have no bizarre or unusual requests, its just that my views are different from theirs and they are unmoveable on their own views. They have told me outright I am wrong (In their eyes) and would not honor my decisions. Please give me any opinions or advice you can offer. Also with the life span increasing and smaller families having been the trend, I am sure I am not the only one finding myself in this position..THANK YOU for any and all help you can offer. take care and GOd bless.