Probably born around 1790 from the census returns, as his age varies from census to census.
1841 census William Pugh, a mason Age: 50, born: Merionethshire, Wales. Living in Civil Parish: Llanelltyd with Catherine Pugh 50 and children Gwen Pugh 15, Hugh Pugh 14, John Pugh 9, Anne Pugh 7
1851 census William Pugh, Age: 64, born: Llanfachreth, Merionethshire, Wales. Living at Tynyceunant, Garthgynfawr, stonemason, Catherine Pugh 60 (his wife), Ann Pugh 17 (house servant).
1861 census Name: Catherine Pugh, Age: 71, born: Llanfachreth, Merionethshire, Wales, is head of household and living with her at Garthgynfawr is only her unmarried daughter Gwen Pugh 37 (given as a cook). Caterine is a widow, formerly mason's wife. So William Pugh has definitely died since 1851.