Auxiliary Bishop of Dublin served under Cardinal Desmond Connell and Archbishop Diarmuid Martin between 1994 and his retirement in 2009.
49-year-old Fr Fintan Monahan will be installed as bishop at the Cathedral of Ss Peter and Paul in Ennis on Sunday 25 September.
Over 10 years ago, Archbishop Martin began promoting the concept of lay people working in partnership with clergy in running parishes.
"All the guys I went to school with are walking away from the Church. We've got to reach out to them, without forgetting older people."
Historic moment for diocese as two married men prepare for ordination.