I've always suspected that they are another race, or beings with magical abilities that we haven't heard of yet... because they are unknown to Alagaesia and/or not spoken of. It would make sense with all the changes going on within Alagaesia at the end of the series. And with Angela being privy to knowledge that almost no one else is. Maybe I'm just being hopeful, but I like to imagine that one or both of them were shapeshifters and that, for whatever reason, they were on a journey for freedom. Whatever the case, Christopher has said that we'll find out the truth in Book 5.