For completeness/clarity here they are c/o FamilySearch;

1841 Buckholt M B, Dixton Newton, Monmouthshire, Wales
Household Role Sex Age Birthplace
William Jayn M 60-64 NOT Monmouthshire
Ann Jayn F 60-64 Monmouthshire

So both born abt 1777-1781.

"M.B" = Mally Brook - see https://en.wikipedia.org/wiki/Buckholt,_Monmouthshire

1851 Dixton Newton, Monmouthshire, Wales
Household Role Sex Age Birthplace
William Jayne Head M 80 Charcoal Carrier Receiving Parochal Relief. Painswick, Gloucestershire
Anne Jayne Wife F 83 Skenfrith, Monmouthshire

So Wm born abt 1771, Anne born abt 1768.

Unfortunately for us these are not unusual names in Dixton area at this time, eg from this site's PRs;

Record_ID: 235207
Entry_Number:
Year: 1849
Month: Sep
Day: 2
Surname: JAYNE
Forenames: Ann
Residence: Monmouth
Age_at_death: 77
Officiating_Minister:
Event: Burial
Cause_of_death:
Memoranda:
Notes:
Register_Reference:
Page_No:
Parish_Chapel: Monmouth
Soundex: J500

So born abt 1772 !?..