So rather than ask whether Bran is The Night King, maybe we should be asking a different question: Is Bran Harry Potter?
That’s why Bran being the Night King is far less likely than the notion that Bran and the Night King are intrinsically linked like another famous magic duo: Voldemort and Harry Potter.
Could Bran be both the Three-Eyed Raven and the Night King?
The Night King marked Bran in his vision similarly to how He Who Must Not Be Named marked Harry when he gave him the lightning bolt scar, creating a connection between Bran and the Night King that can likely only be broken by one of their deaths.