[ThaVirus]

Originally Posted by mr. tegu

The Night's King, who was the 13th Lord Commander, married a white walker. He is definitely not the same as the Night King from north of the wall that we saw get turned into what he is now. At least such a thing hasn't been revealed yet though I guess it could be that way.

This link helps explain it. http://gameofthrones.wikia.com/wiki/Night%27s_King

You could also find a page about the Night King.

From your link:

After he was killed, it was discovered that he had been making human sacrifices to the Others - the White Walkers - and all records of him were destroyed, and uttering his name was forbidden, so it became lost to history. Nevertheless, it is believed he may have been a Bolton, a Magnar of Skagos, an Umber, a Flint, a Norrey, or a Woodfoot, though Old Nan claims to know a version of the tale where he was actually a Stark, brother to the King-in-the-North, named Bran

I guess this and The Door is where the Bran=Night King theory sprouted legs?