The one flying away is definitely Naija and Li's son. If you finish the game without all the memories, after the credits, Naija tells you to go back and try again, as you were too focused on just the facts and not the memories of her childhood..."my son".
With all the memories, that is replaced by the Mia sequence, with the boy touching the memory crystal. As for the long black haired one on the bed, could be another child, but he looks different, and older. Don't think it could be Li, as he doesn't look human at all, and I don't think it is the first son, as he doesn't look half human/half whatever-Naija-is.