Shiny shoes

My friend was visiting from out of town, and I was showing him around downtown a little bit at night. Walking, and trying to remember the very limited trivia I've absorbed about the city thus far, we found the Billy Goat's Tavern and went in for some dinner and drinks.
I remembered reading about the place as a famous hangout for reporters from the Chicago Tribune building across the street, and lo and behold, there were quite a few reporterly looking fellows having drinks at the bar.
We ate and absorbed the journalist brain juice oozing from the dirty walls and left to wander the city some more. We came near the State street bridge over the Chicago River and I was telling Chris about Marina City when we heard a voice.
"Hey man. Hey! Thems some nice shoes. Say-uh lemme shine em for ya."
We turned and saw a black guy in a thin jacket and wearing shiny Nikes coming up. Shine shoes? He spoke really really fast and I noticed that many of his teeth were broken, but some were capped with metal.
When my friend and I didn't immediately walk away, he quickly knelt down and pulled out a cloth and a bottle of shoe shine. He took my friends foot up on his knee, squirted some brown liquid on his shoe and proceeded to shine it with the cloth.
He talked to us the whole time.
He told my friend, "Okay, I got a riddle for you. You answer it, double or nothin, double or nothin."
"Don't do it," I told him. "Don't do it. You'll lose."
The shoe shine guy looked up at me and said, "You talk real fast, where ya from?"
"I've lived in Chicago for a couple years, " I told him.
He finished the shine on both shoes, and my friend and I agreed that they did look much shinier.
The man put his hand out and said something that neither of us understood, but we realized it was money time, of course.
My friend pulled out his wallet, and took the singles he had in it, $3, and was about to give it to the guy when he said: "Seven bucks, it's seven bucks."
"Damn," I said.
My friend laughed and pulled out a $10 bill and gave it to him.

The guy said, "Alright, Imma ask you the riddle. Okay. Now tell me, how many sons did your father have?"

I knew that my friends father was somewhat estranged from him. I asked him if he knew.
He said, "Oh yeah, I know."
I thought about what I knew about him and guessed: "3".
My friend said, "No, 4. I've got three brothers from my dad."
The shoe shine guy said, "Wrong! Shit, you know your dad didn't have no babies! That's what mothers do!"
With that he walked away from us, and we turned to cross over the river and see what else could happen to us in Chicago.