Who is The Boy from Cities of the Plain and what is their importance?

The boy is the shoeshine boy, who stops John Grady on while he is on his way to see Magdalena. He teases John about going to see a girl while wearing dirty boots. Hint taken, he shines up John Grady's boots, and while they talk, the boy describes himself as a black sheep, or an "outlaw." John Grady says he also is an outlaw and black sheep.