Doodle really idolizes his brother, he loves him, looks up to him and wants to keep up with him. One of Doodle's fears is that his brother, who is healthy and strong, unlike Doodle, who suffers from mental and physical handicaps, will leave him behind during one of their adventures.
"Everyone expects Doodle to die, but he defies them all and survives, becoming a loving boy with a strong attachment to Brother. Doodle is pulled around in a go-cart by Brother until Brother teaches Doodle to walk. This achievement, however, seems more important to Brother than it does to Doodle."