I doubt it, unless there is some kind of special agreement. I've seen similar questions in respect of other countries and as I understand it under EU rules, once your pension has been determined that is it. You can't go shopping for a better deal.
Did either of them work in Ireland? Stamps paid in Ireland may give them a partial entitlement to a contributory Irish state pension, in addition to their UK pension, even if they remain living in the UK.
Or if they have no Irish Contributions they could apply for a Non-Contributory Pension and perhaps the Irish Pension office may pay them a top-up to bring the UK pension up to Irish Non-Contributory rate.
This is assuming they have no other income
With only UK pensions , they will have automatic EU entitlement to medical cards without a means test.
If they are in receipt of an Irish social welfare payment they will be subject to a means test for medical cards.
As they are already entitled to a UK pension, the Irish Pension Service will require them to retain it. They will only pay the shortfall.
Assuming that they will qualify as habitual resident in Ireland and that they don't have any other income, they should be eligible for the Irish Non Contributory Pension minus what they are already getting in their UK pension.