Hi there,
That James Williams later marries Janes mother Rachel after John (Jane's father died in a crane accident at the mine) and they have a daughter called Amy.
All the Thomas' come from Nantyglo. I can't find a suitable William James combo on the 1971 in Nantyglo though. Although if that comes under Aberystruth (which I wasn't aware, my knowlegde of Wales is not great!) then I guess it is a definate possible
I have located 9 possible combos in 1871 though, all in Wales, ages vary from born 1862 - 1866 to cater for the age difference from the 91 census (29) to the 1891 marriage cert (25), only 9!!!
William Williams, father James (works in tin plate works) , mother Ann abt 1865 Llanguith, Glamorgan, Wales Son Llanelly, Carmarthenshire or
William Williams, father James (ag lab), mother Anna abt 1865 Penboyr, Carmarthenshire, Wales Son Penboyr, Carmarthenshire.
William Williams, father James (labourer), mother Ellen abt 1866 Llanbedr Goch, Anglesey, Wales Son Llanbedr Goch, Anglesey
William Williams, father James (ag lab), mother Hannah abt 1866 Llanstephan, Carmarthenshire, Wales Son Llanstephan, Carmarthenshire
William Williams, father James (puddler), mother Elizabeth abt 1864 Trevethin, Monmouthshire, Wales Son Trevethin, Monmouthshire
William Williams, father James (labourer, land 10 area), mother Jane (transcirbed as James) abt 1863 Llanwinio, Carmarthenshire, Wales Son Tre Lech AR Bettws, Carmarthenshire
William H Williams, father James (master builder), mother Elizabeth abt 1865 Monmouthshire, Wales Son Monmouth, Monmouthshire
William Williams, father James (joiner), mother Alice abt 1862 Saltney, Flintshire, Wales Son Saltney, Flintshire
William Williams, father James (bargeman), mother Anne abt 1862 Llangyfelach, Glamorgan, Wales Son Llangyfelach, Glamorgan
There are a handful without fathers, with aunts/uncles/grandparents though, I guess he could be one of those..... (knowing my luck he will be!)