Nicholas looked up when he entered. His eyes widened as he took in Gabriel's [his brother's] posture and saw that he was cradling his arm. “What happened?” he asked quickly, setting down the pen and extracting himself from under the paperwork. [I often try to get out from under paperwork, but this sounds like he's literally wedged under it.]
Gabriel sat on the edge of the closest sofa. “You should see the other guy.”
Nicholas stopped in front of him and dropped to one knee. He met his brother’s eyes. “What happened?” he asked again, accustomed to Gabriel’s humor and ignoring it.
“I made a new friend,” Gabriel said lightly.
Nicholas sat back on his heels. “Are you going to make me ask again?”
Gabriel tried to move his fingers and found he could almost make a fist. “I think I met the guy who followed Chris.”
“You fought with him, I take it? Did you chase him off?” Nicholas’ [His] gaze traveled down to Gabriel’s arm. “Is that broken?”
Gabriel gave a short laugh that was lacking in humor. “Yeah, we fought, but I don’t really think I chased him off.”
Nicholas sighed. “Sometimes I want to hit you. Will you just tell me what happened?” [They fought. He didn't manage to chase him off. Weren't you listening?]
Gabriel smiled at his brother. “It’s more fun to irritate you.”
The main problem was that the back and forth between the two people got annoying, especially with the names Gabriel and Nicholas coming up so often. I got rid of a couple lines and four names, which may be good enough.