Possible 1851 Census but a bit confused regarding names you list in your post
William Owen, farmer of Glan y Gors. His son, my gggg grandad,
Owen Williams,

Name Owen Williams
Sex Male
Age 28
Birth Year (Estimated) 1823Birthplace Llanfigail, Anglesey
Marital Status Married
Occupation ButcherRelationship to Head of Household Head
Event Place Llanddeusant, Anglesey, Wales
Event Place (Original) Llanddeusant, Anglesey, Wales
Line Number 1
Page Number 16
Piece/Folio 2522 / 194
Registration Number HO107
Owen Williams's Spouses and Children
Catherine Williams Wife F 38 Llanfachreth, Anglesey
Rowland Williams Son M 5 Llanddeusant, Anglesey
Ellin Williams Daughter F 3 Llanddeusant, Anglesey
Catherine Williams Daughter F 0 Llanddeusant, Anglesey
Jane Williams Daughter F 7 Llanddeusant, Anglesey
https://www.familysearch.org/ark:/61903/1:1:SGCQ-BB1?lang=en