John Henry Stagg was born in St George, Middlesex, England on 27 May 1873. He was the son of John Henry Stagg (1852-1927) and Maria Ann Tozer (1855-1885). Both his parents were natives of London and were married there on September 15, 1872 in St Jude's Church, Bethnal Green.

John had six known siblings: Alexander William (b. 1875), Maria Matilda (b. 1877), Thomas (b. 1879), Charles (b. 1881), Arthur (b. 1883) and Josephine Ethel (b. 1885). After his mother died in 1885, possibly during childbirth, his father was remarried in 1890 to a woman named Mary Quayle, née Benson (b. 1855 in Liverpool), a widow with two children from her previous marriage. His father and stepmother had four children: Frank Hector (b. 1890), Eleanor Hilda (b. 1893), Albert Edward (b. 1895) and Elizabeth May (b. 1897).

John, known as Jack, came from a long-line or mariners and dock workers and his own father was a lighterman, a worker who transferred cargo between ships and quays aboard barges called lighters. He and his family moved from London to Lancashire around 1880 and first appear on the 1881 census living at 13 Arthur Street, West Derby, Litherland. On the 1891 census John is listed as living with his family at 16 Hawarden Street, Litherland and he was described as a railway labourer. Sometime after this John moved to Southampton.

John was married in New Forest, Hampshire in 1899 to Beatrice May Harriet Lewcock (b. May 4, 1879 in Croydon, Surrey). Together they would have one child early the following year, a daughter named Ivy Pearl.

On the 1901 census John and his family are now residing at 35 Cambridge Terrace, St Mary, Southampton and he is now described as a ship's steward. On the 1911 census John is absent, most likely at sea, but his wife and daughter are listed as living at 66 Commercial Road, Southampton.

When he signed-on to the Titanic, on 4 April 1912, he gave his address as 66 Commercial Road, (Southampton). His last ship had been the New York. As a saloon steward he received monthly wages of £3 15s.

At Queenstown John posted a letter to his wife:

Dear Beatie,
Just a few lines to let you know I arrived on board all right, but what a day we have had of it, it's been nothing but work all day long but I can tell you nothing as regards what people I have for nothing will be settled untill (sic) we leave Queenstown tomorrow, anyway we have only 317 first and if I should be lucky enough to get a table at all it won't possibly be more than two that I have, still one must not grumble for there will be plenty without any.

I expect you will have heard about New York breaking away from her moorings through the suction of our ship, it look (sic) as though there was going to be another collision but happily the tugs got hold of her in time. Now darling you must excuse this short note for it's getting late and we have to be up again by 4.30 in the morning and I expect there will be another rosy time with stairs and baggage of course I don't find anything so bad excepting the food and that we have to scramble for like a lot of mad men but that won't last for long when things get straightened out a bit.

Well good night dear, and mind you don't spend all your money. I hope Mrs. Hack will soon be well enough to relieve you of your Charges so that you may have plenty of room to sleep at night.

Love to all xxxxxx Jack.
I made 6d today, what luck

Stagg died in the sinking. His body, if recovered, was never identified.

Following the Titanic disaster John's widow Beatrice never remarried but did receive financial aid from the Titanic Relief Fund. She remained in Southampton and died in 1973 aged 93. His daughter Ivy was married in 1919 to Mark Barnes (1895-1977) and they had one daughter called Muriel (b. 1920 and later Mrs Patrick Fagan). Ivy died in Southampton in 1942 aged 43.