Then why the secrecy with his last name?
--Jonah
--Jonah
My guess would just be to fuel speculation.
Maybe he doesn't have a last name, and was recruited into the First Order as an orphan, or brainwashed to destroy the memories of his identity.
Or maybe he's a product of a post-galactic war baby boom, conceived the night Death Star 2 was destroyed. Finn Yub Nub.
Her staff has lightsaber looking details a the tip, so who knows.
Wasn't it leaked not too long ago that Rey and Kylo are twins (Han and Leia) separated at birth and that they're both Force adepts?
I don't think they have any relation.