Thanks Barbara.
So there are 3 different families in that area:
John Joseph & Hannah
Frederick & Elizabeth
Thomas & Mary Ann
One more family and I can't explain 'sister' Ellen:
Ellen Susannah Relf
England Births and Christenings, 1538-1975
christening: 08 Aug 1855 St. Margaret, Rochester, Kent, England
residence: Rochester, Kent, England
parents: William Henry Relf, Jane
I can't see a RELF to an Ellen/Helen marriage 1861 - 1871.
Henry b. 1851
George Joseph b. 1853
are the only ones born after the marriage who could have married by 1871 census.
This is getting out of hand.
Henry Relf
England Births and Christenings, 1538-1975
christening: 08 Feb 1852 Saint Margaret, Rochester, Kent, England
residence: Rochester, Kent, England
parents: Richard Relf, Sarah
George Joseph Ralph
England Births and Christenings, 1538-1975
christening: 14 Aug 1853 St. Mary, Chatham, Kent, England
residence: Chatham, Kent, England
parents: George Ralph, Sarah Ralph
Neither of those are siblings of Charlotte so I can't see how Ellen can be sister or sister-in-law to Charlotte.