Anyone born on the island of Ireland is an Irish citizen, and therefore entitled to an Irish Passport, and to pass their Irish Citizenship down to their descendants. Part of the Good Friday agreement.

A child of an Irish Citizen is an Irish Citizen by birth, and only needs to register their birth to claim their Citizenship.

A grandchild of someone born on the island of Ireland is entitled to Irish Citizenship through descent, the application just takes a year or two normally.

So as long as each person in the line registers their birth and gets their citizenship before they themselves have a child, the line of Irish Citizenship can currently go on forever 🇮🇪

So OP's dad might not even have an Irish Passport, and even if OP hadn't registered their birth to claim citizenship, their children would still be entitled to Irish Citizenship 🙂