Law
There were two ways out of the underlands: you violated a major law or you left under your own steam. Chris and Justin had done the former, Joey, Lance and JC had done the latter. It was mostly by pure luck that they'd ended up together. It was also by pure luck that they hadn't killed each other.
They'd come close, though. Especially when they first started off together, and dealing with Chris was akin to walking across a greased pole over a shark pool. Chris had reflexes that were inhuman at times and a temper that was lighting quick; there had been more than one time when someone had said something and found themselves on the sharp end of Chris' knives, while Justin chuckled low in his throat.
It'd had been three years as a group and although Chris and Justin had relaxed slightly - they didn't try and kill you if you blinked funny - they still didn't know exactly what had happened, apart from a murder, no details. If asked, Chris would grunt and twitch his knives and Justin just clammed up.
Joey had a faint idea though. Hadn't told JC or Lance but he was fairly sure that Lance had a similar thought. He'd seen him watch Chris and Justin curl around each other at night or when they were just sitting together with a faintly puzzled expression. Joey thought that Chris had killed whoever it was for Justin. To save him. Protect him. Chris would sell them out if anything happened to Justin and it would help get him back.
Joey could understand that. Lance and JC were his everything.