Upvote:1
Why not the short stay 'C' visit (tourist) visa? which would allow them a stay in Ireland for up to 90 days? They can include in the applications a letter from you that says that you will host them throughout their stay and cover their costs.
If you (the family member in Ireland) are funding their trip, in whole or in part, you would have to include your financial details (bank statement, payslips, P60), and your employer letter, along with their own financial details. Underwriting their travels does not relieve them of the obligation to disclose their own finances; indeed, it may raise the bar. They should take care to offer proof of their home country obligations and that they will return there.
Stamp 0 may be an alternative, as it does take into consideration older dependent family members. It is not for long term residence or citizenship but, rather, for those whom INIS approves entry for a limited and specific stay.
For guidance, you could contact such not-for-profit organizations as the Citizens Information or the Immigrant Council of Ireland.
Additional resources:
How to prove that you have significant ties with family in your home country
Should I submit bank statements when applying for a UK Visa? What do they say about me?