"My Nightingale is Singing" is a rare gem by Astrid Lindgren. Not one of her more famous books (even among her short stories, which never made it as big as her novels), it is nevertheless one of her most beautiful ones. When I feel like I need a good cry, this is a book that always does the trick.
Malin - Maria in the English translation - is a girl whose parents have died of tuberculosis, and she's forced to live in the poor house, where nothing is fun or beautiful. Malin can hardly stand it, until she hears the words: "My linden plays, my nightingale is singing..."
Although this is a picture book, it isn't meant for very small children. Buy it for them when they have reached school age and are old enough both to know what an orphan is and to enjoy a really sad story. Or buy it for yourself while you're waiting for them to grow old enough...