The Lean Rider — Cliff Farrell

After the massacre Hardy and Betty Sue were left with only a horse and a knife with which to face the long battle against the wilderness. A seven-year-old boy and a three-year-old girl, stranded on the limitless prairie. They were up against starvation, marauding Indians, savage outlaws, and wild animals. They were mighty stubborn, but the odds were against them—and their luck was about to run out.