Thanks for having a look, Kim, much appreciated.
Anne/Nancy's mum was Letitia Mitchell. The Gallagher (sometimes Gallacher/Gallaher) family were in Ervey from at least the time of the 1831 census and probably earlier. As said in my opening post, I have followed what became of two of her brothers and two of her sisters and am therefore now naturally curious about her, as she was previously unknown to me and unexpectedly popped up on the newspaper entry when I was looking for something else (don't you just love it when that happens
). No such marriage notices seem to have appeared for any of her siblings, and it actually struck me as slightly unusual, in timescale, that one did for her, given they were not a family of any standing as such.
As an aside, William can be 'followed' at Ervey through marriages of his children, Griffiths Valuation and the Valuation Revision books until, from memory, the 1870's, when he likely died (a couple of possibilities in the death indexes). After a gap, another Gallagher family is in the Ervey townland at 1901/1911, but so far I haven't found anything to connect them back to William and Letitia, so it could just be coincidence.
Anyhow, getting back to this thread and the Ritchie trail, it could be that John and Anne/Nancy didn't have children and/or one or both of them died early in their marriage or possibly, like Anne's siblings, they migrated to the mainland or emigrated to America. So far, though, not finding any obvious death for Anne/Nancy albeit a few possibilities for John, so maybe I should look for any possibilities of Anne/Nancy remarrying too. Like you, I am also not coming across any obvious children to the marriage nor seeing the family group on mainland or USA records, albeit haven't had time yet to look too closely in the latter.