Do you have a sister? Maybe if you do, you would know what you can do to each other. You can hide your toys and dolls, pull each other hair and fight all the time.
This is the usual kind of relationship between two sisters. The only difference is that their dolls are living humans. But they are so little that they can be hidden in any place. And why not in someone’s mouth?! Yes, you heard me well – they eat their own toys.
Credit to kingofthegiantess