Cathie,
So you have
Selby on four censuses 41,51,61 and 1871 (Jane on 1881 as widow)
From c1851 to C71 his birth years are 1798, 1799,1799.
C51 has him born Alnwick, C61 Alnwick and C71 born Shilbottle.
Enumerators were instructed to record " Where Born" as
Parish of Birth or Place of Birth. So "born Alnwick" could mean
Parish of Alnwick or Alnwick town. Ditto for Shilbottle. The Parishes of Alnwick and Shilbottle were neighbours ( Shilbottle south of Alnwick)
Assuming
Selby was Anglican, then searching Baptisms of Alnwick ( then Shilbottle) Baptisms registers might turn up his baptism and father, or both parents.
If not Anglican, then you would have to get into Methodist, Presbyterian,
Roman Catholic baptisms in the area.
Some folk look for marriages wherever a couple's first child was born. Richard, born c1830 in Bedlington, from 1841 census looks to be first child, but couple were old enough to have had earlier children, before 1841 census.
Do you know Belford-born Jane's maiden name ?
Michael
Dixon