I am a great niece of John Thomas, born in Rhostryfan near Caernarvon. His sister, Grace , was my grandmother and his niece, Grace Williams , was my mother. I have more information about his sister's family, which may be helpful and would be interested in additional information.
His sister Grace, married Owen Williams and they had 10 children, one died as a child. They lived in Llangefni, Anglesey.