Personal anecdote, there's a lot of your nervous system that is indeed simulating other personas in your head. And the closer you get the deeper the mirroring (children, spouse).

After some catastrophic events, whenever I was smiling, the shape was altered, and took how my ex was smiling (very different facial structure) and triggered hallucinations of her face onto mine and other various emotions. It happens whenever (at various intensities) I mirror her smile.