Mary Esparza-Vela has written a cute book about the relationship between siblings. Of course they happen to be bears, but human children will be able to identify with them.
Molly keeps trying to get her little brother Fritz to try new things, but the younger cub is afraid of nearly everything. However she gradually gets him to try a few things until Fritz manages to overcome his fear of water on his own.
Of course I liked the illustrations by Alexander Morris, who illustrated one of my books.