Alan Jackson has record of John's baptism in Old Windsor on 26 Dec 1812, the son of James and Elizabeth Knibbs. He was baptised the same day as his brother Joseph. It's the record of the baptism that links John and Joseph with this James and Elizabeth Knibbs who we know disappeard from Woodstock, Oxfordshire after 1800.
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John's brother James married Mary Roake's sister, Elizabeth Roake.
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We see John in 1841 living at crimp Hill, Old Windsor with his wife and 4 children:
John Knibbs 28
Mary Knibbs 29
William Knibbs 9
Anne Knibs 7
Henry Knibbs 3
Charles Knibbs 10 Months
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We can see John in 1861, living with his wife, six of his children, and one grandchild at Crimps Hill, Old Windsor:
John Knibbs head 47 Under Gardener Berks Old Windsor
Mary Knibbs Wife 48 Surrey Egham
George Knibbs Son 18 Under Gardener Groom Berks Old Windsor
James Knibbs Son 16 Under Garndener Berks Old Windsor
Thomas Knibbs Son 14 Ag. Lab Berks Old Windsor
Elen Knibbs Daur 11 Scholar Berks Old Windsor
John Knibbs Son 9 Scholar Berks Old Windsor
Edward Knibbs Son 5 Berks Old Windsor
Mary Knibbs Grand Daur 4 Scholar Berks Old Windsor
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We next see him in 1881 living with is wife and younger son at 7 Trafalgar Place, Old Windsor, Berkshire, England:
John KNIBBS Head M Male 68 Old Windsor, Berkshire, England Gardener Unemployed
Mary KNIBBS Wife M Female 69 Egham, Surrey, England Gardeners Wife
Edward KNIBBS Son U Male 25 Old Windsor, Berkshire, England Bricklayers Laborer
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John died in 1887 aged 74.

Mary died in 1886 aged 74.

I understand that John emigrated to Ontario, Canada and married a girl named Mary Ann Smyth in Aug 1888.