I think i'm happy with Thomas now, as born MarQ 1863 to John Mahoney and Margaret (nee Barry), though this means he was strictly Mahoney rather than Manning known as Mahoney.
The prison records as Manning or Mahoney appear to confirm him, though the 1913 court case for neglecting his children suggests he's a hard worker who gives his wife all (or nearly all - can't make out the amount) his wages, and she is the one who drinks. He is also now a stoker at the brickworks rather than a miner.
There is a 1881 census entry as a soldier at the infantry camp, St Botolph in Colchester, Essex, for a Thomas Manning, aged 23 born Merthyr - but no Thomas Manning birth registered in Merthyr (though there is one born in Llangynwyd, Bridgend).
Not so sure about the 1889 Catherine Evans marriage to John Griffiths yet though, although the subsequent marriage of Catherine Griffiths to Thomas Manning in 1896 would match. But Merthyr burials have no record of a John Griffiths burial to match the Merthyr deaths aged 24 in 1891 or 20 in 1893. Nor can i find a married Catherine Griffiths (or them both) in 1891.
Buying the first marriage certificate wouldn't confirm anything i guess, but buying the 1896 Catherine Griffiths to Thomas Manning one might, if it showed Catherine as widowed. I will suggest this to the lady i'm helping.
No luck finding Merthyr births of William (c 1892), Thomas (c 1896), Catherine (c 1898), Evan (c 1902), Susan (c 1906), or David (c 1908) either as Manning or Mahoney or Griffiths, with mmn = Evans (or Griffiths - I have several where mmn is shown as previous married name). There are a couple of Griffiths births with mmn Evans between the 2 possible marriages in 1891 and 1896, but they are a few years out of the census ages.
Rather a struggle now, and very puzzling.
