It comes from the 1911 Census when Joe Barnett is living with the Marks family and it is stated that Joe and Elizabeth have been married for 7 years. However, I think that this is wrong because Free BMD has the marriage in 1902 in Islington, which is where you would expect it as Hyam Barnett was a member of the Board of Management of the North London Synagogue in Islington for 50 years. See:
http://www.freebmd.org.uk/cgi/search.pl?start=1902&end=1902&...
and
http://search.ancestry.co.uk//cgi-bin/sse.dll?_phsrc=Fqq58&_phs...
Hullo again!
I saw an email from Geni saying you had done something to the records of Joe and his marriage -- or something, I can't remember exactly what. But Geni is still showing Joe as b.1879, Betsy as b.1877, and their son as Michael, b 1884. Shurely some mistake?? Joe Barnett is not an unusual name, and Michael was probably the sone of a different one.
I think two Joe Barnett Joe Barnetts have got conflated. The 1902 marriage in Islington, to Elizabeth Barnett Elizabeth Marks (aka Cissie), is of my great uncle. The father of Michael Joseph Barnett Michael Barnett, born 1884 cannot be the same Joe. Possibly too, his wife's maiden name was Elizabeth Lyons, but Freebmd doesn't find a marriage of two people with those names between 1870 and 1890.