Re Husband and offspring of Elizabeth Williams/Griffiths/Addis/Rowe (b c1851).
Elizabeth Griffiths married James Addis, Sept qtr 1873, Chepstow, 11a 4 (28 Sep St Briavels)
Births Sep 1876 ADDIS, Harry. Chepstow 11a 15 (The only 'Harry' in Monmouthshire betw 1873 and 1879, as far as I can find).
James Addis dies/buried 7 Jul 1877. (St Briavels)
Births Dec 1877 Addis, Maud Elizabeth. Pontypool 11a 168. (Birth one year after Harry; 3-5 months after he died; Jas Addis prob never lived to see his daughter).
1881 Census shows only Maud - no sign of Harry, but at age 5+ he may be visiting elsewhere.
https://www.familysearch.org/ark:/61903/1:1:Q2WM-BRW2Could the previously (expertly-done) research on Harry's birthdate (from Canadian records) mean that he 'led a lie' (not intentional perhaps) his whole life, believing that he was born on 12 Aug 1879? Perhaps he was James Addis' son after all?