I think the boy is a best friend for the old man. Sometimes,the old man
said something to the boy just said to himself and encourage himself
enough. The boy also as the third angle to reflect the old man's life,
and by through the old man's innermost thoughts and feelings.
In my opinion, the boy was the one that always standed by the old man.
He was just like a soul friend for the old man because it was also
because of him that the old man could continued his road.