Hi Valentine
I wonder if this is the family in 1861 living in Little Weldon.
RG9/962/23/18
Sarah Gray Head Wid 60 London, Middlesex
Frances Gray Daur Unm 23 Parish St George's Gretton Mill, Nthnts
Sarah Gray Daur Unm 21 Gretton Mill, Nthnts
Ann Gray Daur Unm 18 Gretton Mill, Nthnts
John Gray GSon 7 Gretton Mill, Nthnts
Sarah E Gray Vstr 5 Gretton Mill, Nthnts
There appear to be a number of John Gray deaths in the years 1851-1861, and a number of Hannah deaths all in Northamptonshire, though of course Hannah was old enough to have married or be acting as a servant elsewhere.
And in 1851
HO107/2093/169/47 Gretton, Nthnts
John Gray Shelin (?) Head 54 (Miller) Gretton, Nthnts
Sarah Gray Wife 49 St George, Middlesex
Thomas Nichols Gray Son 24 (Miller) Gretton, Nthnts
William Gray Son 22 (Miller) Gretton, Nthnts
Elizabeth Gray Daur 12 Gretton, Nthnts
Joseph Walter Vstr 49 (Printer Compositor) St Marylebone, Middlesex
Susannah Walter Vstr 45 (Wife) St George, Middlesex
I wouldn't take too much notice of the 'Shelin' as the image is extremely difficult to read.
Hope this may help. Kind Regards - Dave