Every child learns from a young age that they have to share. Some children learn this through interaction with younger or older siblings while others learn it through playgroups and school. Either way, most children eventually learn that it is expected of them to share with other people.
In a family, the older sibling usually has trouble sharing at first. They were the only contender for their parents love and when a new child comes along, that is all changed. They usually are resistant to sharing with a younger child and make sure the younger child is aware of what is off limits; they often make everything they own off limits.
Labels for Laibel, by Dina Rosenfeild, is a book about sharing between siblings. Laibel is a little boy who is tired of sharing everything with his little brother Yossi. So Laibel puts labels on everything he owns. This, of course, makes Yossi mad and he puts labels on everything he owns until everything in their room has either Laibel in green or Yossi in red on it.
When they go downstairs, they find that everything in the downstairs has a blue label on it that says Mother and they are a little upset. Then when the father comes home, his car and briefcase have a yellow label that says Father. After seeing how silly they had been acting, they boys go back upstairs and take all the labels off their things.
I borrowed this book from a 2-year-old boy and had to sneak it out of the house because he sleeps with it in his crib. This book is just one of those books that everyone can identify with. Everyone can think of a time when they did not want to share. It is especially good for older siblings...