I said before that I couldn't find the Evans family before 1911 (when they were at Ffrith-y-Foel) but now had some success! I was looking to close to home, but your info added some clues!
1891 at Legh Street, Golborne, Leigh, Lancashire we have
James Evans, age 32, a Road Labourer, born Rhenllan (I reckon that should be Henllan, which is near Denbigh)
Annie Evans, age 30, born Glan Conway
James Evans, age 3, born Liverpool
William H Evans, age 5 months, born Golborne
also a lodger Thomas Williams, age 27, a Road Labourer, born Dinas Mawddwy
Then have the info you came up with ...
1901 at 3 Trecastell Terrace, Llangelynin, Conwy we have
James Evans, age 41, a Lead miner (there were lead mines in that area behind Conway)
Annie Evans, age 39
James Evans, age 13
William H Evans, age 10
John Evans age 7, born Burtonwood
also a lodger William Owen, age 28, a Lead miner, born Whitford
So ... it seems the Evans family moved around a lot, with various jobs!
Cannot find William H Evans in 1911, he would have been 20, not with parents at Ffrith-y-Foel.