Thomas Algernon Smith-Dorrien-Smith was born on 7 February 1846 at Berkhamsted in Hertfordshire. He was the son of Robert Algernon Smith-Dorrien (died 8 October 1879) and Mary Ann Drever.[2] He was given the name of Thomas Algernon Smith-Dorrien at birth. In 1872 he changed his name by Royal Licence to Thomas Algernon Smith-Dorrien-Smith. His younger brother was Horace Smith-Dorrien. He married Edith Anna Maria Tower (died 17 Jan 1892), daughter of Christopher Theron Tower and Lady Sophia Frances Cust, on 8 April 1875 and they had seven children:
Major Arthur Algernon Smith-Dorrien-Smith (28 January 1876 – 30 May 1955), married on 11 May 1909 Eleanor Salvin Bowlby, daughter of Edward Salvin Bowlby and Elizabeth Vans (née Agnew).
Mary Sophia Smith-Dorrien-Smith (9 November 1877 – 22 December 1948), married on 3 July 1902 Townshend Evelyn Boscawen, son of Rev. Hon. John Townshend Boscawen and Mary Tremayne.
Major Edward Pendarves Smith-Dorrien-Smith (26 February 1878 – 12 October 1937), married on 2 June 1915 Frances Amy Salvin Bowlby, daughter of Edward Salvin Bowlby and Elizabeth Vans Agnew.
Edith Innis Smith-Dorrien-Smith (1 January 1881 – 7 September 1968)[citation needed]
Cicely Frances Smith-Dorrien-Smith (4 November 1882 – 18 April 1915)[3]
Gwendolen Smith-Dorrien-Smith (7 November 1883 – 16 April 1969)[4]
Charlotte Smith-Dorrien-Smith (22 April 1886 – 12 January 1970)[5]