Looking at the 1939 Register there are two Byrne families in Llandudno.
Patrick and Edith Byrne living at 24 Llwynon Road, Llandudno he is a builder, they married 1927 Conway. There are 4 children in the household but their details are officially closed. Edith's maiden name was Jones
Frank & Elizabeth Byrne living at Golf Club Cottage, Glan Y Mor, Llandudno. Frank is a Golf Club Steward, also living with them John Byrne a builders labourer. The details of the children of this household are also officially closed. Elizabeth and Frank married 5/8/1923 Pentraeth, Anglesey. Elizabeth's maiden name was Jones.
Such a pity we couldn't see the children's information, then we could be certain that one of the families are Eric's