His exact parentage is unclear. When he first appears on the 1891 census he is described as the grandson of Mrs Elizabeth Thorn and being described as her adopted "boy" by the time of the 1901 census.
Mrs Elizabeth Thorn was born in Fawley, Hampshire, England around 1834. The identity of her husband is unknown but he is known to have been a mariner and with him had at least four children: Emma (b. 1865), Louisa (b. 1868), Henry (b. 1870) and Henry James (b. 1875). By the time of the 1901 and 1911 censuses she was going by the name of Elizabeth Williams and claimed to be a widow.
The 1891 census shows Harry and his grandmother living at Jones Lane in Fawley, she being described as a laundress. His grandmother was possibly widowed within the next few years and remarried as she is listed as Mrs Elizabeth Williams, a widowed charwoman. Harry, now described as her "adopted boy," is described as a butcher's boy. Mrs Williams was still living at the time of the 1911 census, still at Jones Lane, and she was described as a domestic.
Harry was married in Southampton on 18 February 1908 to Elizabeth Eliza House (b. 1887 in Southampton) but the couple would have no children. Elizabeth is recorded on the 1911 census living at 103 Albert Road, Chapel, Southampton whilst Harry is absent, likely at sea.
Harry Thorn married Elizabeth Eliza House at St. Mary's Parish Church Southampton on 18 February 1908. They lived at 103 Albert Road Southampton.2
When he signed-on to the Titanic in Southampton on 9 April 1912, he gave his name as "H. Johnston" and his address as 103 Albert Rd., (Southampton). He had transferred from the Minneapolis. As an assistant ship's cook he received monthly wages of £4.
Harry Thorn died in the sinking. His body, if recovered, was never identified.
His widow Elizabeth was remarried towards the end of 1913, becoming Mrs Reginald Edwin Marlow. Widowed again in 1930, she was remarried to a man by the name of Harry Chick and she moved to Swindon, Wiltshire. She died in 1959.