Wondered if this might be the family in 1841 Census (HO107 1422 18/14)
Thomas Rees, 50, Copperman
Margaret Rees, 50
Jenkin Rees, 25, Copperman
Mary Rees, 20, Charwoman
Gwenny Rees, 15
Ann Rees, 11
Cecil Rees, 9
Joan Rees, 6
Rees Thomas, 13
Address Underhill Hse, Margam, Taibach - all born Glamorgan.
You are also chasing a Lewis Rees 1827, parents Thomas Rees and Margaret Griffith. But no mention of a Lewis above.
regards