Board Thread:TV Show Discussion/@comment-29325269-20160812000609/@comment-5308269-20160812162241

We don't know that Bran can't have children. In the books, Ned Stark ruminated on the possibility that Bran's injury had made him unable to sire offspring, but that didn't prevent them from making Bran Robb's heir. If being paralyzed was considered an equivalent disqualifier to being castrated, like Theon Greyjoy, from inheriting a lordship, the Stark's would have made Rickon the heir over Bran.

Being the Three-eyed Raven doesn't require one to be stuck in a tree. The Child of the Forest, Leaf, explained in A Dance With Dragons that the "Three-eyed Crow" was in the tree specifically because he was very old. And apart from Bran's gloomy idea of his future, no one actually said he was going to be bound in a tree like his mentor. It's incredible how people can read the chapter, and STILL say "Bran's gonna become a tree"!

One idea about the TV-canon's Night King is that he was originally Brandon of the Bloody Blade. A son of Garth Greenhand (the original king of of the Reach), and the forebear or father of Brandon the Builder. And as a proven greenseer, he might additionally be the reason why there are greenseers and wargs born amongst humans, where originally only Children of the Forest had those abilities.