Sarah Georgina Knibbs' son was baptised George Knibbs (not Turvey) on December 20 1896.
Sarah & Albert Turvey married one month before George was born.

Witnesses to the marriage were Laura Turvey and Albert Knibbs, probably Albert's sister and Sarah's brother.

Albert and Sarah were listed as "full age" bachelor and spinster with Albert from the Brackley parish and Sarah from Swerford.

The marriage record states that Albert's father was John Turvey, a labourer. However, I can see no John Turvey in Brackley in 1881 or 1901, neither can I see an Albert Turvey in Brackley in 1881 with a father named John. However, it was pointed out to me that there is a John Turvey living at Brackley St Peter, Northampton in 1881. He has a son name Willie, so one theory is that Albert William Turvey was called Willie or William within the family.

Checking within the GRO records available at Ancestry.com, I was able to find a record of the birth of Albert William Turvey at Brackley, so that supports the theory that Willie and Albert William are the same person.

The other interesting fact is that this John Turvey also had a daughter named Laura - we know from the marriage records that the marriage between Albert Turvey and Sarah was witnessed by Laura Turvey.

If that is correct, then Albert's family appears as the following in 1881:
John TURVEY Head M Male 39 Whitfield, Northampton, Laborer
Ester TURVEY Wife M Female 34 Falcott, Northampton
James Hy.TURVEY Son Male 14 Brackley, Northampton
Sarah Elizh. TURVEY Daur Female 10 Brackley, Northampton
Laura TURVEY Daur Female 8 Brackley, Northampton
Willie TURVEY Son Male 4 Brackley, Northampton
John TURVEY Son Male 11 m Brackley, Northampton
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We can also see Albert with his wife and children living at Brackley, Northants at the 1901 census. The name has been transcribed incorrectly as Tuney:
Albert W Tuney 24 Norths Brackley Northampton Drayman Brewery
Sarah Tuney 27 Smaford Northampton Brackley
Dorothy Tuney 3 Norths Brackley Northampton Brackley
Eva Tuney 1 Norths Brackley Northampton Brackley

Sarah's son George Knibbs then aged 4 years was living in Hook Norton, Oxfordshire at the 1901 census. He was living with his great-aunt Louisa Knibbs and her husband William Weston.

Born to her parents Humphrey Knibbs and Eliza Rose out of wedlock. She was registered as Sarah Georgina ROSE and given the Christian name of Knibbs when she was baptised. Humphrey and Eliza eventually married, 15 months after Sara was born.
Sarah's name was given as Sarah Georgina KNIBBS when she married to Albert Turvey in 1896.

George was conceived out of wedlock but baptised one month before his mother Sarah married Albert Turvey. George was baptised as George Knibbs. I believe it was quite possibly this George's birth which was recorded at the GRO as George ROSE, during Oct-Dec 1896 in the Chipping Norton District of Oxfordshire (which includes the village of Swerford where he was baptised).
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George is listed as aged 4 years, living in the Civil Parish of Hook Norton, Oxfordshire at the 1901 census. He appears to be living with his great-aunt Louisa Knibbs and her husband William Weston. His parents were living at Brackley, Northamptonshire with their daughters Dorothy and Eva.
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It is quite probable that it was this George Knibbs who was killed in action during the Great War at Gallipoli on Wednesday 8th November 1916. We know from the Commonwealth War Graves Commission that a George Herbert KNIBBS, born in Swerford, Oxfordshire, England was killed on this day, and the records show that the only George Knibbs born at Swerford who could have been killed in the Great War was this George, son of Sarah Georgina Rose Knibbs.

If it was this George, then the CWGC has the following information on him:

George Herbert KNIBBS
Private
No: 17112
2nd Battalion, Hampshire Regiment
died on
Wednesday, 8th November 1916.
Age ?

Theatre of War: Gallipoli
Cemetery: BAGHDAD (NORTH GATE) WAR CEMETERY, Iraq
Grave reference: XXI. M. 7.

Additional Information: (Formerly 18188 2nd Battalion, Oxfordshire and Buckinghamshire Light Infantry, Hampshire Regiment.)
Born: Swerford, Oxfordshire
Enlisted: Bournemouth
Residence: Enstone, Oxfordshire

The Times Newspaper recorded the folowing on 3 April, 1917:

Previously Missing, now Reptd, Died as Prisoners in Turkish Hands
HAMPS R. - KNIBBS, 17112 G.H.(Bournemouth, Enlt.)

The place name in brackets after his name was to identify the home of his next-of-kin.
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There is also reference to George Herbert Knibbs on the War Memorial in the Church at Great Tew, Oxfordshire, (below) to the memory of the men of the Great Tew parish who laid down their lives in the Great War. (Click to Enlarge)