Mr Harry Senior was born in Doncaster, Yorkshire, England on 5 January 1881.
He was the son of Charles Senior (b. 1834) and Emily Louisa Rochfort Sanders, née Godin (b. 1845). His father, an iron worker, was a native of Leeds, Yorkshire and had married his wife Emily, a native of Isleworth, Middlesex, in Doncaster in 1875. Emily had had a previous marriage in 1869 to Henry Sanders (b. 1845 in London) and had one known child, William, in 1873, and she was apparently widowed around the same time.
Harry had four known siblings besides his half-brother William: Charles (b. 1876), George (b. 1878), Ernest (b. 1882) and Emily (b. 1885).
Harry appears as an infant on the 1881 census living at 25 Kelham Street, Hexthorpe, Yorkshire. His father died in 1888 and by the time of the 1891 census he and his remaining family were listed as living at 11 Arbitration (?) Street, Doncaster and his mother was described then as a retired nurse.
Harry later went to sea. He appeared on the 1911 census living at the home of his brother Charles, 102 Thackerary Avenue, Tottenham, Middlesex, and he was described as an unmarried donkeyman, a colloquial term describing a handyman at sea, usually in the engine rooms.
When he signed-on to the Titanic on 6 April 1912, Senior gave his address as 17 South Road, Clapham, (London). He had transferred from the Kingsland and as a Fireman he received monthly wages of £6.
On the night of the sinking Senior was in bed but felt a slight bump at the time of the collision. Curious, he went out to investigate and saw broken ice along the starboard side of the forward well deck. Thinking nothing was amiss he returned to his bunk down below but was not there long when another fireman came yelling that all crewmen should rise and muster to their lifeboats. Whilst on the forward well deck he witnessed lifeboat 1 being lowered which he reported as being filled with only 13 people, only two of whom were women (in fact only 12). He later moved upwards to the boat deck and assisted other crewmen in releasing the two collapsible lifeboats stowed above the officers' quarters and made provisions to get the two boats to the davits:
"I saw an Italian (sic) woman holding two babies. I took one of them and made the woman jump overboard with the baby, while I did the same with the other. When I came to the surface the baby in my arms was dead. I saw the woman strike out in good style, but a boiler burst on the Titanic and started a big wave. When the woman saw that wave she gave up. Then, as the child was dead, I let it sink, too... I swam around for about half an hour, and was swimming on my back when the Titanic went down. I tried to get aboard a boat, but some chap hit me over the head with an oar. There were too many in her. I got around to the other side of the boat and climbed in. There were thirty-five of us on board, including the second officer, and no women. I saw any amount of drowning and dead around us. We picked one man off an overturned boat and he died just as he was pulled over the side. Later the second officer signalled to some other boats and some of us were transferred to them. We sighted the Carpathia at daybreak, after being in the boat about five hours. As soon as I got on board I was put in the hospital and taken good care of."
Rescued atop collapsible B, Harry later described his experiences to The New York Times, the interview published on 19 April 1912.
Harry later returned to sea and was still working on ships into the 1920s. His brother Ernest, a machinist, had married a London-native named Alice Martha Blackman (b. 21 September 1884) in 1904 and had four children: Ernest (b. 1904), Charles (b. 1908), George (b. 1910) and William (b. 1911). What became of Harry's brother Ernest is not clear but Harry and Alice later co-habited (there is no indication that they were ever married) and had three children of their own: Henry Charles (b. 1914) and twins Ivy and May (b. 1916).
Harry died in Deptford, south-east London in 1937 as a result of throat cancer. Alice Senior died on 31 August 1960, also in London.