i’m pretty sure only one actor can be possessed at a time.
you can have the player control dispatch events without knowing who is listening for them. Then the character can bind to those events. In that case then the character has to know about the player controller class, however there are ways to decouple if you really needed to (interfaces, an intermediate class, actor components).
To verify that only one character can be possessed, just remove the player character from scene temporarily and then see if input doesn’t register on the NPC.