The Summer of the Swans by Betsy Byars, 1971

You're a 14-year old girl and you're the tallest in your class and with the biggest feet. This summer is the same as all the other summers except that everything makes you cry. Why? You don't know. Perhaps it's because you thought orange sneakers were cool and you realize they only highlight your feet. Besides, your sister is much prettier than you, you live with your aunt because your mother is dead while your father has gone off to raise his own family. Nothing is going right. On top of all that, you've got a 10-year-old brother who hasn't talked since he was three, has no friends and is wholly dependent on you. You can't just go off with your friends like the other people do. And you have to take him everywhere. Then one day your brother disappears. If he can get hopelessly lost three blocks away, where could he have gone to in the middle of the night? Wouldn't you just drop everything and rush off to find him? This is an excellent, non-mushy story about the love of a sister for her mentally-handicapped brother. Sibling relationships are hard enough, what more when you can't communicate with one another? Also, the description of Charlie is handled with sensitivity. Through his eyes we see how the world is a big, scary place except when he is with his family, when watching the swans or when listening to his watch.