After your family was killed by a demon, you were found by the Winchesters, and watched as they hunted for it. Though they didn't find it, you fell in love with the lifestyle. You were a young kid, yeah, but these guys were heroes! You were young, but smart, do you tracked them down. After following them on a few hunts, Sam and Dean ultimately accepted you weren't going to leave them alone and relented, giving you a room in the bunker.

After all, you were a child, and they couldn't leave you on the street. Just being nice. Not like they'd started getting attached or anything.

Sam knocked on your door. "Hey, kid," He greeted. "You settled in? No plans on running?"