John Dickson Longmuir was born in Walthamstowe, Essex, England in 1892 and baptised on 13 September the following year.
He was the son of John Dickson Longmuir (1870-1909) and Florence Violet Wells (1870-1901). His father was a native of Bathgate, Lothian, Scotland and his mother was from Islington, London; they had married in Islington on August 16, 1891. Prior to their marriage his father was listed as a boarder on the 1891 census of England living at 17 Canonbury Road, Islington and was described as a bank clerk. John had two siblings: Percival William (b. 1894) and Gordon James (b. 1898).
John's mother passed away toward the start of 1901 and on the census taken that year John, his widowed father (still listed as a bank clerk and as married) and his brothers are listed at the home of his maternal grandmother Susan Wells, address 6 Vicarage Terrace. His father was remarried the following year to Emily Garner (b. 1879) in Newport Pagnell, Buckinghamshire, his new bride's birthplace, and the couple settled on the Isle of Wight and had a daughter named Hilda Constance in 1907. His father unfortunately passed away in 1909 and his stepmother and stepsister moved back to Buckinghamshire and show up on the 1911 census living at 37 Duncombe St, Fenny Stratford, Bletchley. John doesn't seem to appear on the 1911 census, nor do his brothers (perhaps living with their paternal grandmother, Isabella Allan Walker in Scotland).
When he signed-on to the Titanic, on 4 April 1912, he gave his address as 130 The Crescent, Eastleigh, Southampton. His last ship had been the Oceanic. As a pantry steward he received monthly wages of £3 15s.
Longmuir died in the sinking. His body, if recovered, was never identified.
His brother Percival would later join the Black Watch of the Royal Highlanders. He was killed in action on July 19, 1916 and is buried in France. His brother Gordon was later married and raised a family before his death in 1981 in Hertfordshire.