Hi Ray.
Thanks for that explanation & research.
My understanding is that Mary Ann's first husband died in a mining accident which I suppose would have been in the very early 1900's & then Edward was born as an illegitimate child in 1908 as a result of a relationship that did not last.
Edward, the youngest child by about 7 or 8 years as I say was born 1908.
David, Thomas & Mags would have all been born between about 1890-1900 so the ones found above are too old, unfortunately.
I suspect that Mary Ann Jones was living in several houses around Mountain Ash as a boarder with some of her children, minus Edward who seems to have been sent to Llantrisant House by 1911. Other addresses I know she lived at were 23 Tyrfelin St & also a house in King St, as well as Gwernifor? St as discussed, all between about 1910 & 1940. I would imagine she would appear in the 1901/1911 census in Mountain Ash or Penwricheiber. I don't think she would have moved far.
I can upload a scan of the full birth certificate if anyone thinks that may help?