When the narrator's little brother is born, he was six and found the baby, "from the outset, a disappointment."
Born in a caul, a membrane that can cling to the infant's head at birth, William Armstrong's head seems to overtake the body, which is tiny and red and "shriveled like an old man's." The family worries that this infant will die--all except Aunt Nicey, who is the midwife, because, she argues, he has the cauls which has been made from Jesus's gown. So convinced is the father that little William will not survive that he is not named until he is three month old, and the father has a carpenter build a mahogany coffin.
The narrator is disappointed because he knows that little William will not be normal. He has always wanted to have someone else with whom he can race, someone to box with, someone to climb trees with--a real brother. But, he is told by his mother that if William Armstrong lives, he will never do such things.