Everything for a Dog by Ann Martin

Bone is a stray dog, all alone in the world, looking for a safe place to call home. Charlie is devastated by the death of his older brother, but at least he has his brother's dog to comfort him. All Henry wants is a dog of his own, and even when his best friend moves away, his parents still won't let him have one. Bone, Charlie, and Henry don't know each other, but their lives are about to connect in a very surprising way. Because dogs, and dog lovers, have a way of finding each other