Hi Sally,
Hope you get this e mail as there were two e mail address's on the rootsweb.
Looked in the Glamorgan 1851 census, as I didn't have a place where either
of them were born I could only go for the age group and there was only one
that the names matched but there were no children. I believe you said a
child was born in 1850 so this might not be your family. I will look up the
1851 Brecon census to see if I can find them there.
Place at time of census Penydarren
Thomas Williams age 23, married coal haulier, born Aberdare 1828
Margaret Williams wife, age 20, born Llangfyhangel Brecon 1831
It might be yours
cheers Rose