Neither of them really died when they were supposed to. They stumble across one other while wandering the wastes sometime after Fallout 3 and decide to travel together. What happens next is totally up to whoever might want to fill this, but I would love it if Israel's connection to the Enclave came back to haunt them in a big way.

(Also, by no means required, but there are some bonus points in it for you if all that radiation has turned James into a Ghoul)