Lord Francis Douglas Marquess of Queensberry; a younger brother, Lord Archibald Edward Douglas (1850–1938), who became a clergyman; and a younger brother and sister, the twins Lord James Douglas (d. 1891) and Lady Florence Douglas (1855–1905), who married Sir Alexander Beaumont Churchill Dixie, 11th Baronet. He was an uncle of Oscar Wilde's lover Lord Alfred Douglas, and a younger brother of John Douglas, 9th Marquess of Queensberry. In 1858, Douglas's father, Lord Queensberry, died in what was reported as a shooting accident, but his death was widely believed to have been suicide. In 1862, his mother, Lady Queensberry, converted to Roman Catholicism and
Lord Alfred Douglas suppressed portions of Wilde's "De Profundis" letter in 1912, Douglas turned against his former friend, whose homosexuality he grew to condemn. He was a defence witness in the libel case brought by Maud Allan against Noel Pemberton Billing in 1918. Billing had accused Allan, who was performing Wilde's play "Salome", of being part of a homosexual conspiracy to undermine the war effort. Douglas also contributed to Billing's journal "Vigilante" as part of his campaign against Robbie Ross. He had written a poem referring to Margot Asquith "bound with Lesbian fillets" while her husband Herbert, the Prime Minister, gave money to