To those readers who have helped with this family:
I have located the Rev. James Hughes Thomas' wife, Sarah Ann Thomas, nee Rees, in 1878. She has died at 9 Queen Street, St. John Cardiff, at the home of her step-son William Hughes Thomas, a draper. The certificate names the informant as W.A.Burton, grandson.
In continuing my research I would now say that this person is William Alfred Burton, technically her step-grandson, descending from Eliza Couzens Thomas and a Scottish baptist minister William Burton. Eliza would have been only 3 years old when Sarah Ann Rees married the Rev. James Hughes Thomas.
Keith Rees Aus