Hi there, could this be them, although Sarah Anns birth date is out by quite a bit?
1891 Census living at 10, Queen Street, Ystradyfodwg,
THOMAS, John Head Married 1846
Colliery Overman Llanwinio, Carmarthenshire
THOMAS, Lydia Wife Married F 43 1848
Dowlais, Glamorganshire
THOMAS, Thomas Son 1869 Coal Miner Aberdare, Glamorganshire
THOMAS, Sarah Ann Daughter Single F 20 1871 Dressmaker
Ystradyfodwg, Glamorganshire
THOMAS, Amy Daughter 1873 Ystradyfodwg, Glamorganshire
THOMAS, Elizabeth Ann Daughter 1873 Ystradyfodwg, Glamorganshire
THOMAS, Leah Daughter 1878 Scholar Ystradyfodwg, Glamorganshire
THOMAS, John Son 1881 Scholar Ystradyfodwg, Glamorganshire
THOMAS, Myfanwy Daughter 1887 Scholar Ystradyfodwg, Glamorganshire