Helping my daughter trace her partner's tree for him for Christmas so taking a few short cuts

Looking for George Mathews (one 'T', age 21, allegedly, at marriage in December 1884) with father William Mathews, occupation at time of son's marriage was glass toy maker - have found the following on the censuses with good match for William on occupation/age:
1881 RG11; Piece: 3009; Folio: 66; Page: 16 George age 18 with William and Jane
1871 RG10; Piece: 3121; Folio: 48; Page: 7 George age 5 with William and Emma
1861 RG9; Piece: 2154; Folio: 116; Page: 5 William and Emma before George was born
1851 HO107; Piece: 2057; Folio: 311; Page: 7 ditto
In 1891 William seems to be a widower in the workhouse infirmary (glass button maker) and there is a death for an Emma Mathews in Birmingham in 1887 and one for an Emma Matthews in 1886 which is a slightly better match for age. So who is Jane or is this an enumerator's error? And why are the ages for George out between the 1871 and 1881 censuses??
Ermy