That's a coincidence then because that particular William senior on the 1911 census was a Tinsmith in Cork as well --and had sons John and William, and a wife named Mary -- might he have married twice I wonder and the previous children been from the first marriage?
Also the William born July 1909 would only be 1 year old on 1911 census as it is supposed to be age last birthday.
Or am I missing something -- probably!