Your brother, Dean, tried to kill Metatron, but the angel rammed a blade through Dean's heart, killing him. However, the mark didn't want Dean to die. It brought him back but as a demon. Sam and Castiel captured Dean and tied him up in the bunker. They left to try and find a cure for him, leaving you to watch over Dean. You are Dean and Sam's eight year old little sister.

"Well, hello, little one." Demon Dean greeted, smirking mischievously.