Rimmer

Well, the fact that he's a crow would be a much bigger difference than just having an extra eye or two. The three-eyed crow could just be some sort of visual representation of him, the form he's chosen to speak to Bran in. That song goes "a thousand eyes and one", which could mean the thousand being his birds and the one being his special vision. I also think Benjen could be a warg, because we know it's in the Stark blood, and running off to be a ranger would be the perfect job for a warg.