Summary from Goodreads:

Little Lord Fauntleroy (1885, 1886) by Frances Hodgson Burnett is a beloved children's novel that made a huge impact on the 19th century public, shaping everything from boys' clothing fashions to copyright law. Cedric Errol is a generous, kind, and exemplary middle-class American boy who is suddenly found to be the heir of the Earl of Dorincourt. Saying loving goodbyes to his working-class friends, Cedric goes to England together with his mother to embrace his new fortune. His grandfather, the old earl, is a bitter old man ridden with gout and a foul temper, trusting no one. However the angelic boy elicits a profound transformation in the grandfather, which not only benefits the castle household but the whole populace of the earldom.

If only the old man's heart would soften toward Cedric's estranged mother, the family would be healed at last. And when another potential heir to the earldom makes a claim, it seems that everything is lost....

But all things are possible through a child's innocent trust, true friendship, and unconditional love.