His parents were national school teachers, Pádraic Ó hEithir and Delia Ní Fhlaithearta.

He received his secondary school education at Coláiste Éinde (St Enda's College) in Galway.

After university, he spent a number of years working as an itinerant bookseller for Comhdháil Náisiúnta na Gaeilge.

He also served as a staff journalist with RTÉ Television, working on the current affairs programmes Cúrsaí and Féach.

He married Catherine von Hildebrand in 1957 and they had five children; Ruairí, Máirín, Brian, Aindriú, and Rónán.