Galton was a naturalist, statistician, and evolutionary theorist. He was a second cousin of Darwin's, having descended from his grandfather, Erasmus. Born in Birmingham in 1822, Galton studied medicine at King's College, London, and also read mathematics at Trinity College, Cambridge. On inheriting a large fortune from his father, he abandoned medicine, which he disliked, indulged in travel and sport, and then financed his own expedition to southwest Africa (1850-52), completing a natural historical narrative of the journey (Galton 1853).

Known to his family as 'Frank', Charles Darwin's seventh child himself became a distinguished scientist. He was an undergraduate at Trinity College, Cambridge, initially studying mathematics, but then transferring to natural sciences.

Emma Darwin, Charles Darwin's wife and first cousin, was born Emma Wedgwood, the eighth and youngest child of Josiah Wedgwood II and Bessy Allen. Her father was the eldest son of the famous pottery manufacturer, Josiah Wedgwood I. Her mother was one of eleven children brought up in a remote country house in Wales. Emma was part of a large and lively extended family, Unitarian in religion, liberal in politics, and with links to the intellectual elite of the country. Her immediate family lived at Maer Hall in rural Staffordshire, a few miles from the Etruria pottery works.

Charles Darwin's cousin, William Darwin Fox, was admitted to Christ's College, Cambridge, in 1824, three years before Darwin; the two men became close friends. They corresponded throughout their lives, exchanging accounts of their growing families interspersed with discussions of Darwin's work. Fox was often asked for, and provided, information from his own observations of the natural world.

A colourful and insightful exchange occurred in 1865 in a light-hearted conversation between Darwin and Henrietta Huxley, the wife of Darwin's friend and colleague, Thomas Henry Huxley. Like her husband, Henrietta was a close friend and great champion of Darwin and his work. She was also, it seems, a keen devotee of Tennyson.

Charles Darwin's readership largely consisted of other well-educated Victorian men, nonetheless, some women did read, review, and respond to Darwin's work. One of these women was Darwin's own niece, Julia Wedgwood, known in the family as "Snow". In July 1861 Wedgwood published a review of Origin entitled "The Boundaries of Science" in Macmillan's Magazine. As a family member and one of the few female reviewers of Darwin's work, Wedgwood's review merits further exploration.

Henrietta "Etty" Darwin (1843-1927) was the eldest of Charles Darwin's daughters to reach adulthood. She married Richard Buckley Litchfield in 1871. She was a valued editor to her father as well as companion and correspondent to both of her parents.

Jane Loring Gray, the daughter of a Boston lawyer, married the Harvard botanist Asa Gray in 1848 and evidence suggests that she took an active interest in the scientific pursuits of her husband and his friends. Although she is only known to have corresponded directly with Darwin once, sending him observations about the behaviour of her dog (letter from J. L. Gray, 14 February 1870), she also passed on information through her husband, and is one of few women cited in Darwin's Expression of Emotions. The Grays visited Charles and Emma Darwin twice, spending several days as guests at Down House in October 1868, and visiting again in August 1869. Although they never met again, the two couples became close friends.