In what context?
Consent to switch off life support? Authority to make funeral arrangements? Person to be consulted /advised in an emergency?
There can be conflicting persons who could be described as next of kin. The usual pecking order would be
1. Spouse
2. Non dependent offspring if no spouse
3. Parent - if no spouse/children
4. Brother/sister if none of above
mf
Certainly, all 3 of your contexts are relevant to me. Here is my case...
Elderly relative with 5 offspring ie the 5 siblings.
A sibling is the next-of-kin (NOK) and is worse than useless. Original NOK was changed as she moved out and married, living 20 km away. The new NOK is only 1 km away from parent.
NOK rarely answers her mobile phone. Parent fell down stairs, but still managed to activate alarm. NOK had phone off.
Parent is immobile, high dependency, needs 24/7 care, in hospital since Easter. NOK wouldn't even discuss nursing home option, delayed the process for several months. This is the only option now and a nice nursing home bed has been secured mainly by efforts of other siblings.
During the hospital stay, there were a few emergencies and NOK could not be contacted.
NOK collects DSP pension for parent. It is not being lodged to bank.
As far as switching off life support, Doctors have broached this subject, as it will become relevant within a year. NOK would prolong life at whatever cost.
I suppose the logical solution is for the parent to change NOK, but parent is too submissive.