Hi Marglos
Apart from Elizabeth Sarah, William & Hannah CASTLE had the following children baptised in Herne:
1825 11th Aug John
1825 21st Aug John (Note: Repeat of previous entry)
1828 13th Oct William
1830 22nd Aug George
1840 5th Apr Emma Hannah
Notes against all say Herne (Labourer)
Given the gap between George & Emma it's quite likely they had more children baptised in another parish.
The other CASTLE couples were Thomas & Isabella, William & Emma, William & Esther, William & Hester, Charles & Emma, Edward & Hannah, John & Rosina, & Sarah (single women)
Earliest baptism 1818, last 1869.
Only one CASTLE marriage before 1837, that was in 1828.
Six marriages after 1837
A bit more info that might help (or not

) in case any of it fits in with what you already know, at least it shows the CASTLEs were spread across this part of Kent.
There's a note against William & Emma to say he was a Shoemaker.
There are a number of CASTLEs in Upchurch, which is about 21 miles from Herne & there's a John there who is also a Shoemaker.
There are also two couples, in Upchurch, with the surname CASTLE LARKIN, one man is also a shoemaker.
Betty