Glen & Sean,
Sure it's a fine day in Mother Ireland, is it not?
The Catholic Church has for as long as I have loved her has had a process called Annulment. You can go to just about any Catholic web site and search for Annulment. Being that Ireland has recently allowed divorces, information may not be as readily available as it is here in the USA.
Try this site,
American Catholic - A Roman Catholic Church site from the Franciscans and study on from there.
In General, the annulment process is started at the Parish Priest level, Your guy, get to ask the priest to begin the process for him. The Priest then should provide him with a large packet of questions to be filled out by him and members close to him during the time leading up to the marriage and during the time of the original marriage.
These will be extremely personal questions and some be really make him want to chuck it all in, but trust me, these questions are really necessary.
At some point he will be appointed an Advocate, he should accept the Advocates help. He Advocate is a person approved by the Church to be well versed in Canon Law with respect to Annulments.
Eventually, the pile of paperwork will be received at the Bishops Diocese Center, where it will be handed over to the Marriage Tribunal.
The focus of the Tribunal is on the Sacrament Of Matrimonial and whether both parties went into the marriage in harmony with the sacrament.
If the Church can find no reason why the sacrament can be vacated, they then focus on the time of the marriage to find the break that renders the sacrament null and void.
I can not stress hard enough the focus is on the Sacrament of Marriage and not on the Civil aspects. Children of the previous marriage are not considered to be bastards if the marriage had never occurred. The process is time consuming and very introspective and Annulments are granted in more case than not over here.
I served as a lady's advocate far enough into the process where it became necessary for experience in Canon Law which I do not have.
One last note, the Church still does not like or cosider living together as man and wife without the benefit of marriage to be any thing other that sin. I'm just giving you fair waring about that.