Just follow me for a minute....
He grows up believing that Fother is his real mother and that MiB was the chosen one to become the Protector. Warned about the Source and the tragedies to man kind if someone ever went in to get it. Fother finally tells him that she killed his real mom and that MiB is telling the truth.
He accepts his new role as Protector of the Source(forgetting the years of lies from Fother), throws MiB into the Source after being told no one should ever go in there to get it. Bringing all the candadites to the island expossing the Source. If he doesnt bring anyone it would not need Protecting. by doing so, he is forced to protect the Source through Richard and other leaders, Shuns Ben causing him to become irate enough to kill him before he finds a replacement.
Anyone else think that perhaps a Hanso was part of the Others that MiB went to live with, finding the characteristics of the island and passing them down to generations. Might have been a survivor of Fothers death at camp.