Galton married Louisa Jane Butler, the daughter of the Very Reverend George Butler, Headmaster of Harrow School, and sister of Josephine Butler, a prominent feminist and social reformer. The marriage was reportedly a happy one, though they had no children.

Galton maintained a close relationship with his cousin, Charles Darwin. Darwin's theory of evolution profoundly influenced Galton's thinking, particularly in his work on heredity and eugenics. Galton admired Darwin's scientific rigor and intellectual curiosity, and the two engaged in frequent correspondence and discussions.

Galton was actively involved in various scientific and intellectual societies, including the Royal Geographical Society, the Royal Society, and the Anthropological Institute of Great Britain and Ireland. He interacted with leading scientists, intellectuals, and social reformers of his time, exchanging ideas and collaborating on research projects. He was known for his sociability and his ability to engage in stimulating conversations.

Galton and his wife Louisa never had any children. Historians suggest various possible explanations, including concerns about Galton's health or a deliberate choice not to have children due to his eugenic beliefs. Galton himself expressed concerns about the potential for hereditary defects to be passed on to offspring.

Francis Galton died at his home in Haslemere, Surrey, at the age of 88. He was buried in the Darwin family plot in Downe, Kent. His death marked the end of a remarkable life dedicated to scientific exploration and intellectual pursuits.