This is AMA's definition of
Independent Historian:
"Independent historian(s): An individual (eg, parent, guardian, surrogate, spouse, witness) who provides a history in addition to a history provided by the patient who is unable to provide a complete or reliable
history (eg, due to developmental stage, dementia, or psychosis) or because a confirmatory history is judged to be necessary. In the case where there may be conflict or poor communication between multiple
historians and more than one historian is needed, the independent historian requirement is met. The independent history does not need to be obtained in person but does need to be obtained directly from the
historian providing the independent information."
So, a patient's next of kin could be considered an independent historian if s/he provided additional history when the patient can't.
EDIT: It doesn't seem like if someone comes in solely to interpret that it would count.