I couldn't see Thomas & family back in 1851, but there were other Sumpners in that area who were also Corn Millers ....
But 'mum' is there in 1841.
HO107/Piece 1343/Book: 3 Folio: 40; Page: 28 Leeds, Sheffield Street
Thomas Sumpner 30 Corn Miller
Elizabeth Sumpner 30
Ann Sumpner 9
Thomas Sumpner 1
PS. Just noticed that in 1881, John W is enumerated both with Selina/Selena as Household Head, and with Stepfather and his Mother's family (shown married tho')