After finishing Gail Sheehy’s new memoir, “Daring: My Passages,” I revisited “Passages,” her hugely influential 1976 pop-psychology best seller about the stages of adult life. There I was surprised to be reminded that she had a brother, and that he’d been killed in Vietnam. He appears nowhere in the 484 pages of the new book, despite an early chapter about her childhood and detailed attention to her sister and parents. Of course, no memoir can be entirely comprehensive, particularly one by a person with as storied a life as Sheehy, who, in her spectacularly successful journalistic career, has written about everyone from the Maharishi Mahesh Yogi to Margaret Thatcher and Hillary Clinton. Still, it seems a strange thing to leave out.