Kieran was born in Youghal in 1951. He was educated by the Augustinians in Dungarvan and from school entered the novitiate of the Order. After theological studies in Rome he was ordained in 1976 and came back to Ireland to teach for a while in New Ross. 

However, he soon returned to Rome, where he studied Scripture at the Pontifical Biblical Institute. In 1989, he began his academic career as a lecturer in Scripture in the Milltown Institute of Philosophy and Theology. While there, he began his PhD studies in Trinty College Dublin, studying under Prof. Seán Freyne.