For reference, 1881 census:
https://www.ancestry.co.uk/interacti...=successSource
Hill Street, Rhos, Ruabon, Denbighshire
William Jones Head Mar 50 Coal Miner Ruabon, Denbigh
Sarah Jones Wife Mar 40 Do
David Jones Son Unm 19 Coal Miner Do
Absalom Jones Son Unm 16 Do Do
Mary Jones Daur Unm 15 Scholar Do
Wm Thos Jones Son Unm 4 Do Do.
The big age gap between Mary and Wm Thos suggests that Sarah could be a second wife, or that Wm Thos could be a grandson rather than a son. Or adopted / fostered? (I can't find an obvious birth reg for him with MMN Bellis at the moment.)