Thanks osprey,that does indeed rule out the GRO record for John Henry that I obtained,there doesn't seem to be any other GRO record that fits.
Thanks also Ladyhawk ,he is the Rhodda I am interested in.I found him in the 1891 census--
33 Llamm Street,Camarthen
Jane Williams,head,widow,60,shopkeeper,with 3 boarders,and John Rhodda,boarder,22,single,collier,born Aberdare.
Now mystified,that original 1871 census entry may hold a clue ??