Margaret Davis/Arthur Hebden - Dublin

Hi. I'm looking into my mother's side of the family after she sadly died just before Christmas. My grandfather was Arthur E Hebden (born Nov 1904 in Seaforth, Lancashire, England). He divorced my grandmother Nellie Nina Hebden (was Little) on 2nd November 1949 (registered in Ilford, Essex). He married Margaret Davis on 16th January 1957 at St Marys Chapel (RC), Mulberry Street, Manchester. He was 50, she was 52. They are both buried at Dean's Grange Cemetery, Dublin. Arthur died aged 78 on 14th June 1982 with his address listed as 67 Waterloo Road, Dublin. Margaret died on 26th May 1990 also at Waterloo Road, but strangely there's no age stated and I've searched for her birth record (which I presume is Irish) to match the age on the marriage certificate but can't see a trace in the UK or Ireland? As I understand it she had a brother(s) who were priests? I am just curious as to why there's no sign of a birth record and whether they had any children (before they were married as they were in their 50s). I only remember meeting them once, when I was around 8 or 9 (I'm now 54). My mum had quite a complicated family background and her biological father Arthur, didn't marry her mother until she was 10 and then divorced her seven years later. Being a merchant seaman he did live in various places such as Southampton and Liverpool but also had strong connections in Ilford, Essex. I'm just trying to piece things together to put everything in perspective and feel a sense of appreciation of knowing my roots and also closure. My mum didn't find out she had a half sister until her biological mum died in 1992 so it's all very complicated!
Thanks for reading :)