Now this is interesting, this is the entry which fits best in 1891 and they are living not too far distant from Silvester Street, you can see both places on
www.streetmap.co.uk Unfortunately we don't know when his father John died, although there are a number of entries in the death index which could fit both John and Ellen since I don't find this family altogether in 1901, but I would think that Ellen is the mother of young David but not of the rest of the children.
85 Fontenoy Street, Dale Street, Liverpool
John McCarthy Head Head M 44 Labourer Foundry Ireland Kinsale
Ellen Wife M 31 America N York
John Son 15 Shopboy Port Liverpool
Elizabeth daur 13 "
Ellen daur 11 "
Margaret daur 10 "
Annie daur 5 "
William Son 7 "
David Son 1 "
RG12/ 2907; Folio 16; Page 6
Despite all the children using the same name McCarthy, it might be worth keeping in mind where William's name comes in the list - ie after a younger sister, this just
might be an indication that he is Ellen's child and not one of the original McCarthys.
You need to start looking at the 1881 census for yourself at
www.familysearch.org.
Does the occupation of John the father match that given on the marriage certificate, they often given an occupation despite stating deceased. Are any of the witnesses any of John's siblings to confirm this family?