I wonder if someone could assist with a family that have disappeared off the 1841/1851 census.

I have them on the 1861 and later ....
Edmund Griffith (1801) Merthyr , his Wife Rachael (1808) NK, Glamorgan, David (1839) Merthyr, Edmund (1851) Merthyr.
They are living at 2 Wyndham Street, Merthyr on the 1861 census - and Edmunds occupation is Cordwainer. David & William are both Hauliers
Many Thanks ......