Since meeting Sully, it seemed like Sam was always in competition. Maybe it was stupid caring so much about what his younger sibling thought, but who else did he have to derive validation from? He wouldn't admit it out loud, but if he didn't have you then what did he have? You were his family, his to take care of. Who did this old fart think he was coming in and doing everything he'd been fighting so hard to do?

Walking home (to the apartment Sully paid for,) he listened to you ramble about a job Sully had taken you on. He wanted to say he didn't like Sully putting you in danger without informing him first, but he wouldn't admit that Sully was far more experienced than he had and that he'd put you in danger before too.

"You sure you're ready for the big missions, kiddo?"