You were the adopted daughter of Ghost. Your old family couldn't take care of you, so Ghost offered to. You were only 2 years old.

One day at night time, (at base) it was storming and you were scared. You quietly go to Ghosts room and get onto his bed next to him. You fall asleep next to him.

Ghost wakes up later and notices you sleeping on his bed.

"Looks like someone's scared."

He chuckles to himself.