It is a conjecture that Anthony's wife Mary was indeed Mary Veasey. It's a conjecture that the marriage that this is the correct marriage although it seems most likely.

Anthony can be seen at the 1871 census living at Aston, Birmingham, Warwickshire, England with his wife Mary, at the home of his father Richard Knibbs.
Richard Knibbs abt 1807 Swinford Oxfordshire Head Aston Warwickshire
Anthony Knibbs abt 1848 Swinford Oxfordshire Son Aston Warwickshire
Mary Knibbs abt 1848 Birmingham Warwickshire Sister-in-law Aston Warwickshire
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The 1881 British Census shows Anthony and his family living at 2A Vine Place, Dart St., Aston, Birmingham, Warwickshire:
Anthony KNIBBS Head M Male 32 Swerford, Oxford, England Chandelier Maker
Mary KNIBBS Wife M Female 32 Birmingham, Warwick, England
Albert KNIBBS Son Male 9 Birmingham, Warwick, England Scholar
Fanny KNIBBS Daur Female 6 Birmingham, Warwick, England Scholar
Lizzie KNIBBS Daur Female 3 Birmingham, Warwick, England
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Anthony can be seen at the 1891 census living at ,"Crabbs Cross, Model Cottages", Ipsley , Warwickshire, England.
Anthony Knibbs,Head,M,43,,Cycle Fitter,Employed,Swerford Oxfordshire,,
Mary Knibbs,Wife,M,,43,,,Birmingham Warwickshire,,
Louisa Knibbs,Dau,,,13,,,Birmingham Warwickshire,,
George Knibbs,Son,,6,,,,Birmingham Warwickshire,,
Fanny Veasey,Ma-Law,W,,72,,,Exion Staffordshire,,Place born may be Erion

I suspect that Louisa in 1891 above is probably the same as Lizzie who was listed in the 1881 census.

The 1901 census shows Mary living at 3 Victoria Terrace, Aston, Birmingham, Warwickshire with daughter Fanny and son George.
Mary Knibbs 53 Wid Birmingham  
Fanny Knibbs 26 Single Birmingham Cycle Fitter
George Knibbs 16 Single Birmingham Brass Fitter
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The 1891 census shows that Mary was the daughter of Fanny Veasey, born abt. 1819 in Staffordshire. Fanny can be seen as a widow in 1881, living at 95 Pope St., Birmingham, Warwickshire, England

At the 1891 census, Fanny can be seen living at 57 George Street, Kings Norton, Balsall Heath, Birmingham, Warwickshire, aged 16 years and working as a General Domestic Servant in the household of Charles Hibberd and his wife Sarah.

Agnes died as an infant.