Entitlement to Irish citizenship is determined by the Irish Nationality and Citizenship Act 1956, as amended, under which Irish citizenship may be obtained by birth, by descent, or by naturalisation.
If a person or their parent was born on the island of Ireland before 1 January 2005, they are an Irish citizen and they can apply for an Irish passport without making an application for citizenship.
My Department is responsible for processing Foreign Birth Registration (FBR) applications for people who are born abroad and claim Irish citizenship through a grandparent born in Ireland or through a parent who has claimed citizenship also through FBR or naturalisation.
Further information on citizenship is available at my Department's website: www.ireland.ie/en/dfa/citizenship/
In regards to the specific individual about which the Deputy has enquired, the Passport Service cannot offer definitive advice in the absence of an application or any further information. However, the person is advised to make an application, submitting a letter outlining the details of their specific situation as well as any evidence they may have of their entitlement to Irish citizenship. The Passport Service will review the application and will follow up with the applicant directly as appropriate.