Croeso i Rootschat!
I was trying to put up the 1891 results (which, in my case, came off a CD produced by the Glamorgan Family History Society) but had trouble with the computer and was beaten to it

William's mother was actually Gwenllian, she was listed as head of household, which suggests she was a widow, though she is listed simply as married. She was born at Drefynnog, Breconshire.
So was Elizabeth Davies, a dressmaker, who was said to be 'deaf and dumb'.
Of the three daughters, Catherine and Gwenllian worked as barmaids, while Elizabeth was a dressmaker. Catherine was born at Cwmdare, the others in Merthyr Tydfil. William was down as a scholar.
Hope this fills in a few more details.
Gareth