I had another look at the 1891 census and I cannot find William or Mary Ann.
Here are details for Everett
Everett J. Howlett, head,m,36, railway labouer, born Peterborough, Nothamptonshire
Catherine Howlett, wife, m, 37, born Aston Clinton, Buckinghamshire
Thomas W. Howlett, son 7, scholar, born Battersea, London
Gertrude A. Howlett, daughter 4, born Battersea, London
Regards
Apache