The third-century Greek biographer Diogenes Laërtius stated that one of the favorite sayings of Antisthenes was, “The fellowship of brothers of one mind was stronger than any fortified city.” Laërtius also recalled an anecdote about Socrates—when asked by a young man if he should marry or not, the philosopher replied, “Whichever you do, you will regret it.”

The Book of the General Laws and Liberties Concerning the Inhabitants of Massachusetts, passed in 1647 and published the following year, contained capital law number fourteen, stating that a “stubborn or rebellious son” could be put to death.

William and Henry James’ younger brothers, Robertson and Garth Wilkinson, were both wounded during the Civil War—they enlisted in the second and first black regiments at the ages of seventeen and sixteen, respectively. When the fifth sibling, Alice, who suffered from various psychological ailments during her life, died in 1892, Henry cabled William the news. William responded, “I telegraphed you this am to make sure the death was not merely apparent, because her neurotic temperament and chronically reduced vitality are just the field for trance tricks to play themselves upon.”

“I must admit, ‘the Mitfords’ would madden me if I didn’t chance to be one,” Diana Mitford—the sister who had wed the leader of the British Union of Fascists in 1936 at the house of Joseph Goebbels—wrote at the age of seventy-four in 1985 to her youngest sister, Deborah, who had married Andrew Robert Buxton Cavendish, 11th Duke of Devonshire, in 1941.