It's nice to share your belongings with siblings.
Mason just got a new toy set and is playing with them in his room when his sister comes in and asks to play with him.
Mason wants to play with his new toys.
Mason invites his sister to come play with him.
Mason tells his sister to leave and plays with his toys alone.
Mason and his sister invent a new game with the toys which they play every day for over a year.
Mason get's bored of the new toys and loses interest after a few hours.