If we grant that each different human, animal, lifeform, etc. corresponds with a distinct (if impermanent) subjective sentient perspective, then I think it's clear that "personhood" simply implies the existence of any such sentient perspective.

And since "free will", in an absolute sense, is obviously folly, that's really all a person is - a sentient perspective, and nothing more, nothing less.

Although sentient perspectives, aside from being merely able to "witness" events, also appear to be inherently "reactive", "willful", or "forceful", the "will" of any sentient perspective is obviously not "free" in an absolute sense, and really is just like any force of nature, like gravity or electromagnetism.

Sentient perspectives (i.e. "persons"), therefore, can be thought of simply as just the "nodes" through which physical forces act and react with each other in spacetime.