People do move. A person could be born in one state and then move away for good even at a very young age. I don't see how that would be an issue. I would say that it would be matter for the courts.e.g. If you ex-spouse was born in the State of New York and your divorce was granted in Florida, due to domicile the GRO will not recognise the divorce.
The OP could easily go the UK where the divorce would be recognised on production of the divorce decree without question of where the other spouse was born and marry again. Ireland would then have to recognise that marriage?