I found this picture made for Knockaround Guys in Google:
As you can see, this one is based on Vin Diesel's character, Taylor Reese (more specifically, Taylor's relationship with Matty. I know this because of how it says "How many friends can you trust with your life?" at the top. Taylor does indeed protect Matty like he protects no other. And in the end of the movie, he jumps in front of bullets to save Matty. He risked his life for the guy and that is indeed something you can't expect out of an average friend. I think Taylor's feelings go beyond friendship, but they are friends, nonetheless.)
Then you can see Matty, smoking a cigarette while he watches Taylor.
Then Marbles and Scarpa are way in the background, because this is based on Taylor and he doesn't really care for either of them. He's pretty much just interested in Matty.
Matty smiling and laughing at Taylor's jokes, appearing to be genuinely happy for a moment:
He is handsome/hot/cute. It's nice to see a smile on that face. He's a different person when he's like this, with Taylor, not so worried or anxious, and he doesn't have to play his father's role.