The "Little Boy" is one of the very first Hosts every created and is a version of Robert Ford as a boy.
He is first seen alone in the desert however, and is assumed to be a Host. He remains far away from the actual park and has interacted with Dr. Robert Ford. The little boy and Dr. Ford have many similarities and one could assume that possibly the child could be a young clone of the doctor himself. He is portrayed by Oliver Bell.
His interaction with the Man in Black in the canyon could indicate that there is more than one "Little Boy" hanging around ready to pop up when someone needs directions, or some water.
The Little Boy asks Robert Ford if he's lost. He says that they're on holiday and that his Dad said they could do as they pleased. Ford invites the Boy to go on a walk with him and the boy accepts the invitation.
Bernard discovers the Little Boy, "Robert" with the rest of his family, including his Greyhound dog. They are all first generation Hosts and are currently off the grid. The Little Boy says he killed his dog, because "Arnold" told him to.