I am Irish and divorced, though not living in Ireland. I have an uncle (and former aunt) who are now both in their late 70s who are separated (as divorce wasn't legal at the time their marriage broke down and neither one could be bothered as time went on). More in my own generation and up to the mid 60s in age, I have a few divorced cousins. Come to think of it, a great uncle of mine had his marriage annulled, before divorce was legal back in the days of King Edward VIII, when annulment was a huge deal. I knew of someone else who had an annulment, in the 70s. Annulment was very much the preserve of the wealthy though. (My dad's family got away with a lot of things that would have been frowned upon if they had had less money. My grandad once marched the whole family out of Mass, and carried on open warfare with the PP for most of the late 1920s and 1930s.)
I agree with Oik that in some circles marriage is a status symbol and divorce just wouldn't be done except by true rebels or people who were prepared to completely opt out of the lives they knew, because they would be dropped like hot potatoes, especially by insecure female friends. The Irish status-conscious middle classes are the most sheep-like people in the world and the herd instinct is very strong. My sister knows a lot of couples who 'own' several mortgages that are all in negative equity -- on the surface they are prosperous people who managed to hang onto their properties through the crisis but underneath many of the husbands are working M-F in London to pay 90% more monthly than what their properties are worth. There are a lot of surface-level charades being played out in Dublin right now, lots of 'show' in financial and relationship matters. Ireland is a country where 'face' is important. It is quite Asian in that respect.
I know quite a few divorced Irish women and men who are my age, but also a lot of women who were always single mothers, whose children were born the year after the Leaving, plus some who decided to have children as single mothers once their careers were established, with partners both male and female. I know people who separated for a while but got back together again. I know 'serial monogamists' who have children with three different fathers. I know someone who thought having a child with her BF would make him leave his wife and his existing children for her. I disagree with IrishDad that Irish people give children and relationships more thought, in general. Those couples I know who live together have decided to do so mostly because they have cast off all the trappings of organised religion. I think many also thought their own parents' lives were a sham, outwardly conforming to the expectations of the church but roiling underneath.
These would be mostly people I went to school with. I grew up in the south side of Dublin, went to a convent primary and community school for secondary. 'Residual Catholic influence' was most definitely in full retreat on the south side of Dublin even in the 70s and 80s. I knew fellow students even in the late 70s whose parents were separated. The people my sister knows would be fellow parents from an expensive all girls' school in an expensive postal code.
I remember having insane debates with my mother during the divorce referendum era and banging my head on the wall at her insistence that essentially marriage exists as an entity regardless of how completely unmarried one or both parties to it behave habitual drunkenness, wife beating, cheating, incest, etc once two people married then 'the marriage' existed as an entity. She couldn't conceive of the terms 'good marriage' or 'bad marriage' having any meaning. Marriage was marriage, and that was that. Once it existed, you put up with it, and to hear her talk, in most cases it was a grim and joyless affair.
She told stories from her childhood observations of young women from poor small farms being married off to old men with bigger farms, women who were practically chained to the kitchen sink and never allowed any autonomy or say in how money was spent, women whom my granny used to feed and support because their husbands drank every penny from the farm and women whose lazy, feckless husbands lost their farms because the banks foreclosed. I honestly couldn't equate any of what she said with a sacrament and neither could she. But she still thought divorce was not right and that its existence would threaten 'marriage', which she considered to have its own existence separate from the lives of the actual people sentenced to lives of misery within its walls. Much the same thought as those opposing gay marriage had I suppose.
One of the things that made her think a bit about her cast iron notions of duty and fulfillment of expectations was the fact that a cousin of hers left the priesthood, sick to the teeth of how his diocese was run, years before the sex abuse scandals hit the news. Priesthood was another of those immutable/written in stone things that she assumed you were stuck with for life. It turned out not to be so.
Many years later I broke the news to her that exH and I were splitting, and she couldn't have been more supportive of my decision. It broke her heart that I would have to sell my house (the law where I am treats the house as a marital debt that must be paid off if there is a mortgage) and my children would lose their home. I think there is a strong Irish attachment to 'home', which perhaps explains the reluctance to uproot children through divorce, or to change their lives in a significant manner -- with less income, etc. available to them than a married couple would have.