« Reply #2 on: Sunday 15 October 06 18:50 BST (UK) »
I've had a look for Catherine's first marriage and found a couple of possibilities on FreeBmd
Dec qtr 1900 Pontypridd vol 11a pg 907 John James Riordan and Catherine Ann Lewis on same page.
June qtr 1909 Merthyr Tydfil vol 11a pg 1281 Catherine Elizabeth Lewis on same page as Sydney Charles Riordan.
My first thought was that the Catherine from 1900 would be too old to have a child in 1923, but I found this likely looking couple on the 1901 census -
16 Lower Church St, Mountain Ash RG13/5005 folio 49 pg 42
John J Riordan head mar 26 coal hewer b. Bishopsgate, London
Catherine A wife 21 b. Beaufort, Mon
So not beyond the bounds of possibility for this Catherine to be having a child in 1923. No way of checking if the other two are a couple as I haven't spotted any Riordan births after 1911 when the mother's maiden name shows on the index. Haven't spotted a Riordan death either but Freebmd isn't complete after 1910 or so and then you have the war to contend with. The marriage cert of Thomas Henry and Catherine is definitely the way to go - with any luck it will give ages rather than just 'full age'. I'll have another look through the full index when my eyes have recovered from the Joneses. If you have any info on older brothers and sisters, it would help prevent eye-strain.
Cornwall: Allen, Bevan, Bosisto, Carnpezzack, Donithorn, Huddy, James, Retallack, Russell, Vincent, Yeoman
Cards: Thomas (Llanbadarn Fawr)
Glam: Bowler, Cram, Galloway, James, Thomas, Watkins
Lincs: Coupland, Cram
Mon: Cram, Gwyn, John, Philpot, Smart, Watkins
Pembs: Edwards (St. Dogmael's)
Yorks: Airey, Bowler, Elliott, Hare, Hewitt, Kellett, Kemp, Stephenson, Tebb