I think the 1871 is the family - you said that Winifred's mother was Gwen and that she died in childbirth - compare brother Thomas and John, the father, on both censuses.
Ann might well have been working away by 1881 - she would be 14 - old enought then.
This might be Gwen and her parents in 1861:
Trawsgoed mawr, Rhos y ? and Nant Heulog, Llangwm
RG09/4310/4/4
Robert Roberts, 63, farmer of 55 acres
Margaret, 62
Hugh, 23
Gwen, 24
Robert Edwards, servant, 11
All b. Llangwm
Have a look through every thing and see if it fits. I don't see a marriage for winifred and Charles so far.
gnu