Hi
Looking at further census records Ambrose W Lovell's wife is an Annie, a Harriet Watts is also boarding in the same household in 1891.
Have found a record in 1891 of
John A Williams b abt 1855 Chichester, Sussex
Katherine M Williams b abt 1858 Wolverhampton, Staffordshire
Kate E Williams b 1887 Wandsworth
Gertrude W Williams b 1890 aged 11 months Harrow, Middx
all living in Wealdstone.
Is this your John Williams?