Thank you so much for looking. It is possible that they married later, as going on the parish baptismal records I think it is likely that they were together from at least 1813 - so Owen would have been 26 and Catherine 30 but that assumes that all of their children were born in the parish.
The following children were all registered at Beddgelert to Owen Owens and Catherine (wish I could look at the original entries):
Owens David 1814 — 1814 Wales Births & Baptisms 1541-1907 Caernarvonshire, Wales
Owens Anne 1817 — 1817 Wales Births & Baptisms 1541-1907 Caernarvonshire, Wales
Owens Henry 1822 — 1822 Wales Births & Baptisms 1541-1907 Caernarvonshire, Wales
Owens Hugh 1824 — 1824 Wales Births & Baptisms 1541-1907 Caernarvonshire, Wales
Owens Anne 1827 — 1827 Wales Births & Baptisms 1541-1907 Caernarvonshire, Wales
Owens Jane 1829 — 1829 Wales Births & Baptisms 1541-1907 Caernarvonshire, Wales
Looking on the 1841 census there is no sign of David or Anne but a Griffiths has appeared who wasn't baptised in Beddgelert (can't find a record for his birth either but that's another conundrum to be unpicked at a later time)
Owen Owens Male 53 1788 -
Catherine Owens Female 57 1784 Caernarvonshire, Wales
Griffithes Owens Male 21 1820 Caernarvonshire, Wales
Henry Owens Male 19 1822 Caernarvonshire, Wales
Hugh Owens Male 16 1825 Caernarvonshire, Wales
Ann Owens Female 14 1827 Caernarvonshire, Wales
Jane Owens Female 12 1829 Caernarvonshire, Wales
Catherine passed away in 1849 and by 1851 it's just Hugh and Jane at home with their dad and a couple of farm hands.