There are 8 children to a dying mother. most of the kids agree to allow hospice and allow nature to take it's course. Out of the blue, a sibling has a medical POA and wants medical attention to continue. no one was aware of the POA.
The hard part is over.
I'm matching you with one of our specialists who will be calling you in the next few minutes.
There are 7 of us. We were never able to get Mom to do an Advanced Health Care document or assign POA. Financially it doesn't matter -- no assets to speak of, nothing to manage except paying for her newspaper, etc. Medically, the nursing home she is in and the hospice organization both wanted a "main person to contact." And it turned out to be most practical for that to be the same person. I'm it. This on a practical level gives me medical POA status. I work closely with my three sisters. (We pretty much leave the brothers out, since that matches their interest level.) We had lots of discuss about hospice and were divided, until a crisis forced our hand. If I made a decision about a drug or a care that my sisters were opposed to, I think we would have a lot of stress in our lives. We try for consensus, but I take responsibility for communicating decisions.
If Mom can still understand what it means to assign someone to act in her behalf, encourage her to do that now.
If a medical POA is not possible at this time, then somebody is going to have to make decisions. If the majority of you can agree on who that should be, move forward on that basis.
What kind of document does the sibling-come-lately have? Is it something Mother signed long ago? Is it notarized? If it turns out to be valid (which doesn't sound likely) Mother can still change it, if she is cognitively able to.