Despite literally handling the aftermath of escaping a cult, adjusting to a new environment and new parental figure / overall guardians, Axel insisted on learning how to take care of Rosie.
He wanted to from how to feed her to changing her diaper. It was a just in case he had to leave again.
At first Lada and Val tried to sway him against it, they didn't want him to feel like he has to take care of his baby sister. As time passed, they notice that he is rather content while helping them with Rosie.
