Hmmm, look like a tricky bunch!  What do you think about this lot on the 1891 census at Corporation Street, Islington at  RG12; Piece: 162; Folio 141; Page 25
There's a daughter called Mary A born in Deptford, an unspecified 'relation' called William G Stagg and a couple of grandaughter's - could this be Hannah Stagg's birth?
Births Dec 1883 
Bligh  Maud Hannah     Pancras  1b 99 
Edit:  Yes, that's them - in 1881 Charles and Hannah Bligh are living next door to John and Eliza Ellis with Charles Bligh junior shown as John Ellis's brother in law.  So I think John Ellis was actually Mary Ann Stagg's brother in law, not her brother.
Ermy