Timothy's Quest — Kate Douglas Wiggin

Timothy Tarbox, a dewy-eyed orphan united in misery with his little sister Samantha. The kids are taken in by maiden lady Vilda Cummins, an old battle-ax who allegedly hates all children. It takes some doing, but Timothy and Samantha eventually win over Vilda, whose bark (as suspected) is far worse than her bite. A romantic subplot involving grown-ups Martha and David never intrudes too long on the sentimental main story.