Mr William Campbell was born in Belfast, Ireland (modern-day Northern Ireland) on 22 September 1891.

Coming from a Presbyterian family, William was the youngest child of William Campbell (b. 1845), a seaman, and his wife Sarah, née Hawthorne (b. 1847) who had married at Sinclair Seaman's Church near the Belfast docks on 25 February 1870. His father was from Belfast whilst his mother hailed from Islandmagee near the port of Larne in Co Antrim. 

His parents went on to have eight children, losing two in infancy, and William's known siblings were: Mary Hawthorne (4 November 1871-1877), Elizabeth Corry (b. 6 December 1873-1912), Sarah (b. 20 March 1876), Mary Hawthorne (b. 24 April 1878), Robert John (b. circa 1882) and Jane (b. 15 October 1884).

The 1901 census shows William and his family living at 47 Spamount Street in the New Lodge area of north Belfast. By the time of the 1911 census, the family had shifted to 45 Earl Street in Clifton, also in north Belfast and William was described as a joiner. The family later moved to 28 Earl Street.

William, described as a "bright lad," was one of the nine-strong "guarantee group" of Harland and Wolff employees chosen to oversee the smooth running of the Titanic's maiden voyage.

William Campbell died in the sinking and his body, if recovered, was never identified.

Just one day after his death his elder sister Elizabeth Leathem died aged 38; she was buried in Belfast's City Cemetery on 18 April.

WILLIAM CAMPBELL
... an apprentice joiner, who was one of the special staff on the Titanic sent by the builders, and whose name, unfortunately, is not included in the list of survivors. As already recorded, a sister of his passed away in Belfast a few days ago, and in her last illness was touchingly anxious to see again her young brother, who all unknown to her had met a cruel fate.  - Larne Times, 27 April 1912

Campbell's estate, worth a meagre £10, was administered to his father William on 28 March 1913. On 15 April 1913 a memorial appeared in the Belfast Newsletter:

CAMPBELL--In fond and loving memory of my dear brother Willie, who lost his life in the R.M.S. Titanic on the 15th April, 1912; also my dear sister Lizzie (Mrs Leathem), who died the following day, and was interred in the City Cemetery.

William's mother later lived at 84 Corporation Street, Belfast and she died as a result of cancer on 20 June 1915.