Coming from a seafaring family I was firmly convinced, as are many others, that a ship's Captain could marry people. However I recently read that although this could be done it would have no legality in the UK or many other countries. However, whatever the validity, the Captain would certainly have given them some sort of certificate. I have not had the chance to go into this in depth so cannot be dogmatic - but if you are talking about particular people, if this is the case, they could have had a certificate from the Captain saying he had married them on his ship but later found it had no validity wherever they were going and just discarded it. I suppose it is also possible that if they settled somewhere in the backwoods the local authority just accepted they had been married somewhere without bothering too much about the evidence - or even had accepted a Captain's certificate without realising it had no value in law.