There are elements that suggest it could be a true story. For example, Max's curious nature and Ruby's responsible yet sometimes bossy attitude are things that can be seen in real siblings. The simple daily activities they engage in, like Max playing with his toys in his own way while Ruby has plans for him, seem to be inspired by real - life family situations.
Well, in a sense it is. The stories capture the essence of how siblings behave. Max is always getting into things and Ruby is constantly trying to keep him in line or get him to do what she thinks is right. It's a very relatable scenario that could be drawn from real - life experiences of families with young children.