Dear Robert
The other directories that are in both Cradiff Library and the GRO are the Kelly’s, and Piggots and they cover the years in between census records and post 1901. They may only contain an odd line or so about the occupants residences or work positions but added together with other details can form a helpful timeline.
Do you know the ships names and years that John was in service?
Sea Captains had, and still do have powerful rights in the abscence of a chaplain over births marriages and deaths when at sea. Their word is law and they would have compiled records of those who sailed with them and where they went .
He would have taken exams to gain his position and his mariner record will be in Archives – do you have this information?
Have you been able to trace all the relations to present day?
Do you have Johns family BMD certificates?
Do you know where they are buried – is it possible they are in the Allenbank graveyard in Cathays? This is run by Cardiff City Council and I can let you have the address if you like, as my rellies are there too.
Cardiff Council will have minutes of meetings held at the GRO - it is possble that the Foreshore Dispute came up at some point.
The Duchess of Cornwall and Marquis of Bute records may hold some clues, as this was whom the dispute was with.
Was there a family bible somewhere or did Frances keep any records or diaries of the times she opened the gates and who she let through each night?
Records pre Cardiff may be in the Pembrokeshire record office seing as he was 30+ when he came to Cardiff.
I know that sounds a lot of things to look for but even if you get a few details off each of these it will gain to you a comprehensive time line. I will have another look tonight.