Aliza has known Andrew since he was a baby, and has always been a mother figure to him. Seeing what has happened to other people in the "Smiley Medical Center" facility, she could bear the terrible thoughts of what will happen to a baby. So, she swore to protect his innocent soul and promise a way to escape together. Overtime, she has adapted ways of carrying the little boy everywhere she goes, such as letting him ride on her back.
As the boy grew older, she knew the hardship that were to come, especially the insanity Andrew had to go through for a long time.
I has this idea in my head for a long time, and I thought they're both cute.