Bran Stark is NOT the Night King and Game of Thrones has given 3 reasons

Warning : Possible spoilers ahead

Ever since Game of Thrones' season 7 finale premiered, theory that Bran Stark is the Night King is doing the rounds. Starting from King's landing to beyond the wall Night's watch (Nah! that Icy Cold hearted Night King has blown down it), everyone has started to believe that Bran is the Night King but George Martin (Author of GoT) has given 3 reasons to prove that the theory is a complete rumour.

Guys, if you remember season 4 which was mainly focused on Brandon Stark and it was shown that Bran is a 'Warg'. In GoT world precisely, warg are people with the ability to enter the minds of animals and perceive the world through their senses and even control their actions. In addition to that, Bran got super natural powers and can have the visions from past with the help of old trees and he can even control humans like he did with Hodor. So here are the 3 reasons.

First, Ned Stark, who had known the secret of Jon Snow, is dead and to unearth this secret, George Martin needed someone to go back in the past and disclose it to the people. Season 7, Bran has disclosed it to Sam Tarly that Jon Snow is the prince who was promised i.e. A Targaryen.

Second, Third Eyed Raven, before passing the sentence for execution of Little Finger, Sansa gave so many reasons that why he must be executed and Little Finger like a crying baby told that you were not there but Bran quoted him what he exactly told when he showed the dagger to Catelyn Stark. Bran brought Sansa and Arya together against Lord baelish and this could have been done by someone like Bran. Apart from this, Bran is constantly watching the developments happening in the world of westeros and helping Jon to have track of it.

Third, least but not the last, Viserion, the third child of Mother of dragons and now a wight dragon, is not only the conveyance of the Night King but he is the destroyer of 'THE WALL'. It will not be easy for Daenerys to ride against him and Night King who has killed viserion in one shot. That's why, Bran will rise and fly. Bran will control the dragon for sure and he will save the winterfell and westeros. 

Its obvious because bran is so harmless in the show. It will all be unraveled in Season 8 but we have to wait until then.