Same family as Joburg found in 1881. The Morgans are enumerated twice at top and bottom of family, any connection to Sarah?
If this is not the correct family, maybe they left for Ireland?
1871 - RG10 Piece 5392 Folio 51 Page 7
31 Duffryn, Merthyr Tydfil
John Dynon 30, filler blast furnaces, Ireland
Sarah Dynon 32 wife Merthyr
John Dynon 8 son "
Michael Dynon 6 son "
Thomas Dynon 3 son "
Mary Dynon 1 dau "
Ann Morgan 62 lodger, wid, Carmarthen
Daniel Morgan 20 son, Merthyr
Cas