Hi there, welcome to the forum.
In the 1929 street directory there is only one Llewellyn Williams - the Rev. Llewellyn (Welsh Cong) at Fron, Church Walks) he was the Pastor at the Independent Church in Deganwy Avenue (not sure where this is - or was) however in the street listing he is H Williams.
Also, going by the information provided, I had a look on ancestry and found a listing for David Roberts from Llanfihangel on the 1911 census at Ty Fry Old Road, listed as widowed, a joiner with a son and daughter Annie 33 and Evan 31 born in Nefyn (occupation Blacksmith Striker) and two sons David Nefyn 24 and Hughie 22 born in Tydweilog
If it was the same Annie she would have been in her late forties when she married, and Evan would have been born in 1880
hope this helps