William Henry James Slight was born in Southampton, Hampshire, England on 30 August 1875.

He was the son of William Henry Slight (b. 1836), a house decorator, and Mary Bryant (b. 1837). His father hailed from Southampton and his mother from Ashton, Kent and they had married in Sussex in 1864.

William had six known siblings: Clara Ann (b. 1866), Jessy Kate (b. 1868), Alice Mary (b. 1870), Henry James Bryant (b. 1871), Mary Jane (b. 1873) and Harry John (b. 1878).

His father died sometime around 1880 and when William first appears on the 1881 census he, his widowed mother and siblings were listed as living at 3 Browns Cottages in South Stoneham, his mother Mary described as a charwoman to support her family. His mother apparently died sometime after this and when the 1891 census was taken William, his brother Harry and sister Mary were listed as living at the home of their married sister Clara Poynter and her family at 39 Bevois Valley Road, South Stoneham. William and his brother were described as errand boys.

William was married in Southampton in 1897 to Catherine "Kate" Lawes (b. 1875 in Southampton) and they had one child, a son named Henry William John (b. 17 September 1898)

William would be absent from the 1901 census and apparently already at sea but his wife and son would be listed as living at 5 Gordon Avenue, Portswood, Southampton. The 1911 census would show his wife and son still living at this address but William would again be absent. Also listed at this address as a boarder was another Titanic crewman, Harry Stubbings.

William's wife Kate died at the beginning of 1912.

William was on board the Titanic for her delivery trip from Belfast to Southampton. When he signed-on again, in Southampton, on 4 April 1912, he gave his address as Hillside, Bitterne Park, (Southampton). His last ship had been the Olympic. As larder cook he received monthly wages of £7. Also serving aboard the Titanic, as a third class steward, was his brother Harry Slight.

William Slight died in the sinking. His body, if recovered, was never identified.

His son Henry was married in 1924 to Emily Elizabeth Painter (1902-1980) and had one daughter. He died in Southampton in 1977.