It seems that Virginia Spencer Carr holds the field in John Dos Passos biographies with her 1984 Dos Passos, favorably reviewed here, in the New York Times, by Kenneth Lynn. If you know one thing about Dos Passos, it's probably that, as a young man, when he was writing the five books on which his reputation as a major American novelist rests--Three Soldiers, Manhattan Transfer, and the USA trilogy (The 42nd Parallel, 1919, and The Big Money)--he was a political radical, and that on the other side of midlife he became a reactionary conservative who campaigned for Goldwater and Nixon. Now that I know just a bit more about him, I'm inclined to think the evident instability might be attributed to a really crazy family story.
His mother, Lucy Sprigg, a Virginian growing up in the years following the Civil War, married at age 16 one Ryland Randolph Madison, a relation of the fourth president as well as an alcoholic slacker. They had one son (not the writer), whereupon James Madison's relative walked away and wasn't heard from again. At this point in the story, one may be expecting a tale of heroic Lucy holding things together: what she did, however, was hand off the baby boy to her own mother and move from Petersburg, Virginia, to Washington, D.C., where her father ran a real estate business. She went to work for her dad and learned, of necessity, that he was not devoted to her mother. She soon met a Portuguese immigrant and successful lawyer, John R Dos Passos, who had married for money, or social prestige, the daughter of a bank president before becoming a success himself. The author of the USA trilogy is the offspring of the lawyer and Lucy Sprigg, his mistress of 25 years. The boy was called Jack Madison by his mother, who told a story about having accepted the responsibility of raising him from a desperate unwed mother in Chicago. The boy's father found it most convenient to maintain Lucy and young Jack in Europe, away from the up-and-up family in D.C., and the writer later deployed the phrase "hotel life" to describe his boyhood. His father would visit on his frequent European vacations, and as a teenager Dos Passos began using his name. He was sent to Choate and Harvard. The USA books are full of restless wanderers, failed and sham marriages, and people from all classes, none of them particularly admirable but the affluent grasping and scheming and outright repugnant.