Old men and unrelated little girls

The best examples of these are in three pieces of literature. First in George Eliot's "Silas Marner", Silas, a miser through losing faith in human nature, loses his treasured hoard of gold. But soon after, he discovers the golden haired Eppie on his hearth & lavishes all his pent up love on her. Fortunately she reciprocates his love & even foregoes wealth & status later to stay with him.

In Victor Hugo's "Les Misérables", Cossette is discovered & rescued from an unspeakably miserable situation by Jean Valjean, & brought up lovingly by him, but gradually becomes cold & uncaring to him on the arrival of her lover, Marius when her  romantic love overrides filial love.

In Rabindranath Tagore's "Kabuliwala", an itinerant Afghan peddler, befriends a little Bengali girl, who reminds him of his daughter. He lavishes his love on her, which she reciprocates. But he is framed on false charges & imprisoned for many years. After his release, he returns to her on what happens to be her wedding day & sadly she has completely forgotten him.

This was brilliantly filmed by Tapan Sinha in Bengali, the little girl played by none other than the sister of the actress who later became a star in Bengali & Hindi films, Sharmila Tagore. It was also made, not so effectively, in Hindi by Bimal Roy.