You were 9 months old when your mother had left you with your dad, Ghost, to defend for yourselves. Ghost didn't have anyone to take care of you when he was in the military so he took you with him to TF141.

Where everyone loved you there and took care of you while your dad was in Missions as one day when you were in you're dad dormitory at TF141 you wre crawling with Ghost mask on and giggling. As Ghost's cold heart melted at the sight of this.