Robert Millar was born in Alloa, Clackmannanshire, Scotland on 7 July 1885.
He was the son of James Millar (b. 1856), a clerk, and Mary Harley (b. 1859), both Alloa natives.
Robert was one of seven known children, his siblings being: John (b. 1881), James (b. 1882), Catherine Brenigan (b. 1883), Jessie Watson (b. 1888) Mary Harley (b. 1889) and William (b. 1893).
The family appear on the 1891 census living at 11 King Street, Alloa. Robert's father died on 29 December 1895 and his mother never remarried. The family were still living at King Street by the time of the 1901 census but the household was now under the control of Robert's wage-earning siblings John, James and Catherine. John worked for the Inland Revenue, James was a clerk and Catherine a housekeeper. Robert was described as an apprentice engineer. Their mother, described as an annuitant on the census, passed away only weeks later on 15 May 1901.
Robert received his education at the Burgh and Sunnyside Public Schools under Mr John Ferguson. On leaving school he was apprenticed to Messrs. Archibald Jeffrey & Sons of Alloa, marine engineers, where he obtained an excellent knowledge of engineering. During his apprenticeship he attended science and art classes and was the recipient of many prizes for his talents.
In 1905 he left Messrs. Jeffery with a special recommendation as a turner and went to the Argyll Motor Works, Alexandria. His next post was on the Tyne with the Wallsend Slipway and Engineering Co. Ltd., where he remained until 1907 and then went to sea on board SS Johannesburg of the Bucknall Steamship Lines, Ltd, and served in that vessel as fifth, fourth, and third engineer. In 1908 he obtained his second engineer's certificate, and served in the same Company's vessel Katuna in that capacity. He obtained his chief's certificate in 1909.
He commenced service with the White Star Line around 1910 and he joined the Olympic as sixth engineer. He was on board when during that ship's collision with the HMS Hawke.
He joined the Titanic as fifth engineer at Belfast on 26 March 1912 for the delivery trip to Southampton. When he signed on again, on 6 April 1912, he gave his address as 59 North Street, (Southampton) and his previous ship as the Olympic. As extra fifth engineer he could expect monthly wages of £9, 10s.
Robert Millar died in the sinking. His body, if recovered, was never identified. He reportedly led an exemplary life and was very desirous of obtaining his extra chief's certificate and becoming a Board of Trade surveyor. He was also engaged to be married to one Lillian McDougall. Robert's family, including his fiancée, benefitted from the Titanic Relief Fund.
He is remembered on the family grave stone in Sunnyside Cemetery, Alloa. His last surviving sibling, Catherine "Kate" died in 1982 in Fife, Scotland and reportedly continued to play Nearer My God, to Thee on the piano even in her advanced age in remembrance of her brother.