Mr John Borthwick Crosbie was born in Croydon, Surrey, England in late 1866 or early 1867 and his birth was registered in the first quarter of 1867. 
He was the son of a Scottish father, Adam Borthwick Crosbie (b. 1840 in Edinburgh) and an English mother, Margaret Bookless (b. 1845 in Woolwich, Kent). He had three siblings, Grace Bookless (b. 1865, later Mrs Marshall Henry Hutchinson), Helen Luke (b. 1870, later Mrs Thomas Doherty) and Adam Bookless (1872-1872).

John first appears on the 1871 Scotland census living at 362 Castle Hill, Edinburgh, Midlothian when his father was described as a brass finisher. His mother died in 1872, possibly due to complications from childbirth; his father was remarried in 1879 to Midlothian native Jane Murdoch (b. 1855) and together they would have three more children: Robert Murdoch (b. 1880), Adam Borthwick (1883-1964) and Marion Greig (1887-1969, later Mrs George Robertson). 

On the 1881 census John is listed with his family, including his new stepmother, at an address in Newington, Edinburgh. He was at this time aged 14 and described as a plumber's apprentice. He is absent from the 1891 census but his family were by then living at 11 East Richmond Street, Edinburgh.

John was married in Hastings, Sussex in late 1896 to Elizabeth Mary Jane Bridger (b. 1867 in Wick, Sussex) and they had two daughters: Marie Frances Margaret (b. 1897) and Elizabeth Catherine (b. 1899), both born in Hastings. The family appear on the 1901 census living at 68 Cambridge Road, All Saints, Hastings and Crosbie at this time was described as a Turkish Bath Steward. 

The family appear to have moved north for a while as his daughter Elizabeth died in Chorlton, Lancashire in 1904. On the 1911 census John and his family were then living at 47 St Dunstans Road, Hammersmith, London and at this time he described himself as a masseur and chiropodist but it is not stated whether he worked at sea at this point.

When he signed-on to the Titanic1 on 9 April 1912 he gave his address as 47 St Dunstans Road, Hammersmith. His previous ship had been the Olympic and as a Turkish Bath steward he received monthly wages of £6, 10s 2.

John Crosbie died in the sinking and his body, if recovered, was never identified.

CROSBIE--April 15th, drowned in "Titanic" Disaster, J. B. Crosbie, of 47, St Dunstan's Road, West Kensington, late of Hastings.
Hastings and St Leonards Observer, 18 May 1912

John's widow did not remarry and she died in London in 1931. His daughter Mary is understood to have married and later died in London in the late 1950s. His father died in Edinburgh in 1922 aged 81.