A mouse grapples with the concepts of brotherhood, species, and family solidarity.A longtime writer for very early readers launches a new series incorporating graphic-novel reading techniques and gentle humor. To introduce the story, the mouse, Figgy, explains how to read panels and the difference between speech and thought bubbles. In the first chapter, Figgy's friend Boone patiently tries to help him understand that they are not brothers. Figgy's a mouse; Boone is a rat. In spite of their similarities, they're different species-cousins. In the second chapter, after learning that a hamster is also a cousin, Figgy uses that label for all his friends. But when Figgy encounters a kitten, Boone has to explain the food chain. In the final chapter, the kitten's mother arrives and captures Figgy. Boone comes to the rescue by providing a distraction, and, in a heartwarming moment, he calls Figgy "my brother" after all. The cartoon animals are depicted with bold outlines and flat colors. Throughout, there are clues as to what might happen next, beginning with the mention of a cat in the introduction. Though different, Boone and Figgy are fun foils for each other. Boone would clearly prefer to be working on more complicated ideas; the illustrations show him working with math and science, but he does take time to sketch out the food chain for his friend. Figgy, in turn, produces "family trees" and a list of his favorite foods. (This book was reviewed digitally.)Satisfying siblinghood in a promising series starter. (Graphic early reader. 5-7)