John FERRIS baptised Aldington 8 Aug 1841 son of William and Elizabeth
http://www.familysearch.org1841 Hurst, Kent
William FARRIS 35 ag lab b.Kent
George 11 b.Kent
Elizabeth 30 b.Kent
Harriot 7 b.Kent
Elizabeth 5 b.Kent
Sarah 3 b.Kent
HO107/478 book 4 page 7
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1851 Burmarsh, Kent
Elizabeth FERRIS nurse wid 40 b.Aldington in the household of William and Sarah CHAMBERS at the Shepherd Hook inn at Burmarsh
HO107/1634 folio 15 page 5
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1861 New Rents, Ashford, Kent
Elizabeth FARRIS head wid 50 shoebinder b.Aldington
John son unm 19 ag lab b.Hurst
Ann BROOKS lodger wid 55 monthly nurse b.Mersham
RG9/512 folio 123 page 20
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From the above and information you already have I would suggest that it quite likely that John was in the following census:
1851 (born Hurst) in Bonnington
1861 (born Hurst) in Ashford
1871 (born Ashford) in Petersfied, Hampshire
1881 possibly in Cheriton Kent (born Cheriton?)
1891 (born Ashford) in Wareham Dorset
1901 (born Kent) in Brentford Middlesex
1911 (born Ashford) in Isleworth Middlesex
At least there appears to be only the one John FARRIS/FERRIS born in Kent around that time and there is only the one appearing in each of the different census years.
So now to try and identify the children and their mother/respective mothers
Casalguidi