I am not doubt going to be way off here but for some reason I see the boy as the main quest giver. Between missions he is your point of contact. He gives you rewards (apples of course) and is the sole source of praise in the game. He will be the one to tell you about the next 'hero' you are helping, what their handicap will be and where you need to go.
Again, that is just how I imagine the stable boy will fit into the game. Maybe as the game progresses, the stable boy's own story become more prevalent and you eventually help him out, working together as a proper symbiotic team.