I can see them in 1851 but the birthplace is Eglwsilan for all the family! - no progress there then!
In 1841 I can find a family with baby Thomas that resembles yours, except that the mother is called Diana. There is a death for a Diana in the same area in Merthyr in June q 1849 though. Ref 26/423 - is she yours, do you know? There isn't a suitable marriage to a Jane after this until 1858, so I think it is unlikely. There are various early Jane/ William marriages in Merthyr but can't tell between them!
What certificates do you have for this family?
I am just thinking that it is difficult to be sure which family is yours prior to 1851 but info from certs would help.
kind regards, Arranroots
