From what I have gathered searching the censuses for this, there are 2 Llanddeusants- Anglesey and Carmarthenshire so it may well be that the enumerator just presumed it was Anglesey.
The Miller's house seems to be occupied by Daniel Watkins' family in 1861 and they are still there in 1871- his widow and family anyway. They are therefore 'next door' to John and Margaret.
What has been bothering me is that there is a 7 yr old Mary G Prichard with the Watkins as granddaughter and in 1881 she is Mary Gwen Pritchard with Thomas and Margaret Williams as niece.
There are too many Williams to try to connect but I did wonder whether that was why John was a Miller for a while. All too tenuous though.
good luck with your searching
heywood
