On FreeBMD http://freebmd.rootsweb.com/
there is a Hector Cecil Peskett, registered March quarter 1902 at Edmonton.
I don't know if this is in the same area as Pancras & West Ham where the other children are registered.
I can't find anything else on him but I don't have access to US records.
The FreeBMD is only an index but gives the parish, page of entry, etc if you want to order the registration to find out parents for sure.
Here is Ellen on 1901 census St Peters, St Pancras, London
69 Harrison Street.
Ellen, boarder,married, 26, b Chatham, Kent
William J, boarder, 4, b St Pancras, London
Edward S, boarder, 3, St Pancras, London
Charles R, boarder, 3 mos, St Pancras, London
They are living with a Julia Sanson, 46, widow, b Scotland.
Interestingly enough, in the column for deaf & dumb, blind, lunatic or feeble minded, there is a tick beside Ellen's name. This puts her birth at about 1875 which is more consistent with some of the other information re her age.
Do you agree that her maiden name was Grant?
On 1881 census www.familysearch.org
there are two Ellen/Nellie Grants b 1874 in Kent that may be your Ellen.
1891 census St Paul Depford, London Ancestry.ca
Ellen Grant, 18, machinist, b Depford Kent
Charlotte Grant, 50, machnist, b as above
living with a George Swindell.
That is the only Ellen Grant b Kent on 1891 census. She is on 1881 census with a Charlotte Grant and some siblings.
Cannot look up much about William John Peskett as there is not time frame for him. Do not see any deaths for him on FreeBMD but it is a volunteer sight so keep checking back. There are no deaths on FreeBMD from 1900-1906 yet. He would have died around 1905 [Stella's birth year] unless he isn't her father.
Re - no Peskitt being married the same time as Ellen Kate Grant could be because it hasn't been transcribed as yet. The indexes are in alphabetical order. I used to transcribe for FreeBMD and am trying to remember how to get to the original records. If I figure it out I will look up and see if William Peskitt is on the same page as Ellen Kate Grant. Can't promise anything!