I've found a John Davies, aged 26 b. Llandysiliogogo but he's listed as a son - no wife.
living: Lochtyn, Llangranog Cardiganshire
Thomas Davies 59 Llandysiliogogo, Cardiganshire, Head, Farmer 100 acres
Mary Davies 55 Llandysiliogogo, Cardiganshire, Wife
John Davies 26 Llandysiliogogo, Cardiganshire, Farmer's Son
James Davies 25 Llandysiliogogo, Cardiganshire, Farmer's Son
Elizabeth Davies 21 Llandysiliogogo, Cardiganshire, Un
Thomas Davies 19 Llandysiliogogo, Cardiganshire, Farmer's Son
Sarah Davies 17 Llandysiliogogo, Cardiganshire, Un
David Davies 15 Llandysiliogogo, Cardiganshire, Son
Mary James 5 Llangranog, Cardiganshire, Granddaughter
Is it possible that he married after the Census?