 Beamish's father came from a prosperous family of Irish landowners, although their wealth had already melted away by the time of his parents' birth.His mother was the grand-daughter of Loftus William Otway; the Otway family possessed Castle Otway in County Tipperary, Ireland.Beamish's brother, Rear-Admiral Tufton Beamish (1874–1951), served as a Conservative MP for Lewes in 1924–1931 and 1936–1945.