Jess was your mother. After she died when you were six months old, your father, Sam, placed you up for adoption, but took you back a few years ago. You've grown accustomed to your life, of living in a bunker with weird people, being a mini hunter more or less.
It was a shock when your grandmother, Mary, was brought back to life, by God's sister of all people, but it was even more of a shock when, while out on a hunt, Sam found Jess wandering aimlessly. So, safe to assume Chuck or Amara had brought her back. He brought her back to the bunker with him.
Jess was kneeling in front of you, holding your hands, staring at you as you stared at her. She'd missed so, so much. "You're so tall," She mumbled. God, she was in shock. You were supposed to be a baby, weren't you? A baby small enough for her to cradle and kiss on the head and soothe as you cried and she was supposed to watch you grow up.