Who is the Three-Eyed Raven?

Game of Thrones 

Three Eyed-Raven:

Who is the Three-Eyed Raven?The three-eyed raven was the last Greenseer, a human living among the last of the Children of the Forest beyond the Wall. Under the guise of a three-eyed raven, he appears in Bran Stark's vision-dreams, following his fall and injury, prompting his quest beyond the Wall and guiding him to the cave in which his real human body resides. There, Bran is trained in the magic of Greensight by the three-eyed raven.

Bran and Three-Eyed Raven:

The three-eyed raven monitors Bran as he experiences a vision of Winterfell during the childhood of Lyanna and Ned Stark that reveals Hodor's true name, Wylis. He tells Bran that it is time to go, but when Bran expresses a desire to remain in the happy memories, the three-eyed raven pulls him out of the vision. He warns Bran to resist the urge to only view those happy times, and reminds him that as powerful as Greensight is, the past is still the past, and cannot be changed.

The three-eyed raven is with Bran when Bran is viewing the events that occurred at the Tower of Joy at the end of Robert's Rebellion. He identifies young Ned's second-in-command as Howland Reed, Meera's father, and also confirms that Ser Arthur Dayne is a better swordsman than Ned is, explaining to a confused Bran that there is a difference between history and what actually happened.

The three-eyed raven continues to guide Bran.

Bran calls out to his future father in desperation – to his shock, Ned seems to hear him, but dismisses it and continues into the Tower. The three-eyed raven pulls Bran out of the vision, and reprimands him again for trying to interact with the past. The three-eyed raven says he's waited a thousand years for Bran, as the weirwood roots have grown into him. He assures Bran that he [Bran] is not destined to share his fate, but warns that he must learn before he leaves. When Bran demands to know what it is he needs to learn, the three-eyed raven declares, "everything"

Eventually, he and Leaf decide that Bran is ready to learn the truth about the White Walkers. The three-eyed raven accompanies Bran into a vision of the distant past, thousands of years ago, during the war between the Children and the First Men, in which they witness a group of Children led by Leaf approach a captured man, and magically insert a shard of Dragonglass into his heart, which transforms him into the first of the White Walkers. Awakening, Bran realizes that the White Walkers were created by the Children to use as weapons against his ancestors.

Later, whilst the three-eyed raven and Bran's companions are resting, Bran interacts with one of the weirwood roots, triggering a vision in which he witnesses a large army of Wights, idly standing in the frozen wastes of the Land of Always Winter. Wading into their midst, Bran stares incredulously at the creatures, ultimately finding himself standing before the Night King himself, and three of his Lieutenants. Unlike the Wights, however, the Walkers take note of their guest. The Night King meets Bran's gaze, and materializes beside him, grabbing hold of his arm. Awakening in terror, the three-eyed raven reveals to him that the Night King has marked him; he knows where he is, and will come for him. The mark likewise neutralizes the magic wards around the cave which bar the Walkers and their minions from entering. The three-eyed raven tells him that he and his companions must leave.

While Meera and Hodor pack their belongings and the children prepare the cave's defenses, the three-eyed raven takes Bran into the past one final time, again to his father's childhood at Winterfell, this time witnessing the young Eddard departing for The Vale, as the castle's citizens look on, including Wylis and Old Nan. Soon, the Night King and his three Lieutenants arrive with an army of Wights to launch their attack on the cave. Though Leaf and the Children attempt to hold them off, their attempts are in vain, as the Walkers and their Wights breach the cave. Still within the vision, the three-eyed raven remains motionless in the roots as the defenders are slaughtered, and Bran, Meera, Hodor, and 

Leaf make their escape through the back of the cave.

The Three-eyed raven turns to dust in Bran's vision, after being killed by the Night King.

Following their flight, the Night King and his two remaining White Walkers enter the three-eyed raven's chamber, and the Night King slowly approaches him. Within the vision, the three-eyed raven tells Bran that the time has come for him to leave. With that, the Night King swiftly executes him, carving him diagonally across the torso with his blade, as the three-eyed raven breaks apart and turns to dust within the vision, leaving Bran alone.

As Bran and Meera were escaping from the wight, a hooded Benjen Stark came and rescued them. When Meera asked Benjen why he rescued them, he answered the Three-Eyed Raven requested him. When Meera said the Three-Eyed Raven is dead, Benjen answered "He lives again." It is a possibility, regarding this answer, that 'Three-Eyed Raven' wasn't a name as first assumed but rather a title used by previous Greenseers before the present time.

My theory:

My theory About Night King and Three Eyed Raven is that i think there's some strong connection between three eyed raven and the Night king,

From I have noticed, you can see in the photo, the Night king used to look slightly similar to the three eyed raven till he was alive, but suddenly when he died and Bran became the three eyed raven, the night king started looking like Bran himself
Is there two night kings..??
Did the 1st one die when he killed three eyed raven?
And if above theory is true,
Then it's possible that If Bran dies, night king dies too.