The son of George Lionel Dawson-Damer and Mary Georgiana Emma Seymour; he married Harriet Lydia Montagu, daughter of Henry Montagu, sixth Baron Rokeby. He succeeded to the title in 1889.

REFERENCES TO Lionel Seymour William Dawson-Damer, fourth earl of Portarlington:

Thomas Creevey to Elizabeth Ord, 24 April 1837 in The Creevey Papers: A Selection from the Correspondence & Diaries of the late Thomas Creevey, M.P. (London: John Murray, 1903)