Hi Prarie,
Had another look at this there seems to be perhaps a couple of mistranscriptions which are maybe throwing you of the trail, but heres what I found
The marriage from 1824 in Raphoe I mentioned in my first post, there are 3 children christened at the same church probably to the same couple:
John Shannon 1833 - father John mother Ann
Elizabeth Shannon 1837 - father John mother Ann
Hugh Shannon 1842- faher John mother Ann
With the gaps in the years there was probably others also that do not appear in these records
I have found a marriage for a James Shannon 1852 Londonderry (CP) married Jane FLYNN, not Fleming, James fathers name is John so seems to fit, although the marriage is recorded in Londonderry CP it may have taken place in Donegal, the civil parish of Londondery stretched into the county of Donegal, there is also a church record for this marriage in Donegal but I can't pinpoint the church. The index for this record is Vol 7 page 3
Regards