In 1901, we can see Henry living in Kent, England:

Henry Knibbs 22 Old Windsor Berks Kent Stoker
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In Memory of
Chief Stoker H G KNIBBS

292484(CH), H.M.S. "Brilliant.", Royal Navy
who died age 37 on 23 March 1916
Long Service and Good Conduct Medal. Son of James and Matilda Knibbs, of 4, Trafalgar Place, Old Windsor; husband of Lucy Sarah Ann Knibbs, of 16, Arthur Rd., Windsor.
Remembered with honour
WINDSOR CEMETERY, Berkshire

Henry joined the Royal Navy on 10 Jul 1899 for a term of 12 years. When he joined he was 5'4" tall with brown hair blue eyes and a dark complexion. His draft record shows the following:
HMS Pembroke 10 July 1899 to 23 Nov 1899 (Chatham Shore Base)
HMS Wildfire 24 Nov 1899 to 16 Jul 1903 (Sloop)
HMS Pembroke 17 Jul 1903 to 27 Oct 1903 (Chatham Shore Base)
HMS Tartar 28 Oct 1903 to 23 Dec 1904 (Cruiser)
HMS Pembroke 24 Dec 1904 to 4 May 1905 (Chatham Shore Base)
HMS King Alfred 5 May 1905 to 19 Jun 1905 (Cruiser)
HMS Pembroke 20 Jun 1905 to 14 Jul 1905 (Chatham Shore Base)
HMS Antrim II 15 Jul 1905 to 19 Jun 1907 (Armoured Cruiser)
HMS Pembroke 20 Jun 1907 to 14 Jul 1907 (Chatham Shore Base)
HMS Tenedos 15 Jul 1907 to 30 Nov 1907 (Battleship/Training Ship in Plymouth)
HMS Pembroke II 1 Dec 1907 to 24 Jun 1908 (Chatham Shore Base)
HMS Agamemnon 25 Jun 1908 to 26 Sep 1910 (Battleship)
HMS Pembroke II 27 Sep 1910 to 30 Apr 1912 (Chatham Shore Base)
HMS Crescent 1 May 1912 to 8 May 1912 (Cruiser)
HMS Dwarf 9 May 1912 to 4 Jun 1913 (?)
HMS Pembroke II 5 Jun 1913 to 24 Aug 1914 (Chatham Shore Base)
HMS Pembroke (Brilliant) 25 Aug 1914 to 31 Mar 1915
HMS Brilliant 1 Apr 1915 to 23 Mar 1916 (Light Cruiser) ^[1]

I'm not sure yet of the circumstances behind Henry's death but we know that he died in sick quarters at Lerwick in the Shetland Islands off Scotland on 23 Mar 1916 with what was described as Otorrhoea Lateral Sinus Thrombosis Embolism.
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^[1]HMS Brilliant, the ship he was serving on, was a Light Cruiser which was deployed off the coast of Ostend and Zeebrugge. It took part in the fighting off the Belgian coast in the first months of the war. The Brilliant was then sent to the Tyne to act as a coastal defence ship, before being used as a depot ship on the Tyne (to 1915) then at Lerwick in the Shetland Isles. During the action off the Belgian coast, HMS Brilliant helped to rescue the pre-dreadnought battleship HMS Venerable after she ran aground.
She was later sunk as a block ship during the attempts to close the ports of Zeebrugge and Ostend.


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Henry was seen to be living at RN Barracks, Chatham, Kent at the time of the 1911 census:
Henry Knibbs 32 M

At the same time, Lucy was living with her step father and her children at 16 Arthur Road, presumably Windsor, but not identified on the return.:
Hughes, William Fredk Head Widower M 48 Bricklayer Windsor Berks
Knibbs, Lucy Step Daughter Married F 30 Eton Bucks
Pearson, May Daughter of Lucy Knibbs Single F 14 Goes to School Eton Bucks
Knibbs, Violet Daughter of Lucy Knibbs F 3 At Home Windsor Berks
Knibbs, Henry James Son of Lucy Knibbs M 3 Months At Home Windsor Berks
Jacobs, Mabel Servant F 16 Clewer Berks

Notes on the census return state that May is Lucy's daughter from before the marriage. It also states that Violet and Henry are also Lucy's children, but born within the marriage.
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Henry and his brother William are both remembered on the War Memorial plaque at the Old Windsor village hall.
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In Memory of
Chief Stoker H G KNIBBS

292484(CH), H.M.S. "Brilliant.", Royal Navy
who died age 37
on 23 March 1916
Long Service and Good Conduct Medal. Son of James and Matilda Knibbs, of 4, Trafalgar Place, Old Windsor; husband of Lucy Sarah Ann Knibbs, of 16, Arthur Rd., Windsor.
Remembered with honour
WINDSOR CEMETERY, Berkshire

I believe Lucy's mother was possibly Frances Pearson who married William Frederick Hughes in q2/1891. Whether this was a second marriage for Lucy or not, I don't know.