I have been trying to make meaningful family connections for Edward and John Roberts.I wonder if "nephew" had quite the more narrow usage we tend to give it today,I have an incomplete set of data that might suggest a relationship as a cousin,but there is no suggestion of a Denbigh birth in it.
For what it's worth:-
John Roberts may be the son of William Roberts seen at Llangynog as follows:
1881 5499 23 23
1891 4602 18 14
William in turn may be the son of David Roberts seen at Pen y Graig,Main
1851 2499 278 3
1861 4262 44 3
This family has an Edward Roberts born circa 1836.
If we then turn to Edward Thomas Roberts,I think he is it this ref. in 1901 with his widowed mother Mary,"Edward T" given as a labourer in a colliery(a miner on his wedding certificate)
Looking for this family earlier the head of the family is an Edward Roberts,given born circa 1839,albeit Denbighshire
1891 4637 101 23
1881 5540 117 26
I can't confidently take this Edward back through 1871 and 1861 to make the connection.He does appear,however to name his (first?) son David,possibly as per his father in the 1851 census(above)
However,if you have access to the 1911 census there is a possible(only possible) connection between Edward Ellis in this census and someone of the same surname with an address as per Edward Thomas Roberts on his wedding certificate.
Regards
Roger