Hi Gail,
Sorry, don't know too much about John Duffy pre marrying Louisa. I haven't had the need to research that side of him yet. Catherine is listed on the 1901 Irish census as the aunt of John Duffy which I reckon would make his mother a sister of Catherine, therefore he was a first cousin of Louisa.
As you know Catherine's husband James (Chetwin) died in 1857 so times would have been hard. Louisa's husband William John Stokes died in 1890 aged just 38, so obviously needs must.
John Duffy's first wife Elizabeth (nee Donohoe) died 13-04-1899 aged 46. Don't know anything about children from that marriage. Before the year was out John had married Louisa and the 1901 census shows Louisa, children and Catherine living with John Duffy.
John Duffy was obviously a man of means having his own business - he was a master chimney cleaner employing several men. In fact, on the 1901 census my grandfather James (Stokes) was an apprentice chimney cleaner. Thankfully, on the 1911 census he is listed as a motor mechanic.
John Duffy died on 21-02-1904 aged 57 by which time Louisa would have been 48. The grave burial details for John and Elizabeth also lists a Patrick Duffy who died 19-04-1918. I don't know if he was a brother or son of John - he would have been 30 when John died so could be either.
Louisa died 14-12-1927 and is buried in the Stokes grave in Glasnevin Cemetery, Dublin with her son James (my grandfather), his wife Maria (nee Fitzpatrick), their son William died young on 08-08-1926 and my aunt/stepmother Ellen who died 21-12-2004 aged 90. Aunt/stepmother is correct - after my mother died in 1966 aged 47, my dad married her sister - my aunt - in 1968.
Finally, as you say Catherine returned to England and died in Toxteth in 1904. Don't know why she was there at that time but that was the area where the Stokes children were born and there may have still been family there.
You may already know but details of census in Ireland pre 1901 are mostly destroyed hence 1901 and 1911 being the first years online. The law in Ireland at present says 100 years must have passed before details can be put online. An attempt was made recently to reduce this to 70 years but was not approved. There was no census taken in 1921 due to the Civil War so you'll have to wait for the 1925 census to go online!
Hope that's not too much to lay on you at this time.
Regards,
PetK