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I located a transcription of the church marriage record on the subscription site Roots Ireland and the marriage was held in the Drumshanbo Church of Ireland church. Drumshanbo is the largest town in Kiltoghert civil parish. Unfortunately, baptismal records for that parish are not available until 1885 and civil registration for births did not start until 1864 so there would be no record for any of the children. There is a civil record for the marriage which would show the names of the fathers of the bride and groom. www.irishgenealogy.ie is a free site which has images of civil marriage records but right now images are only available from 1870-1941. GRO is working to add the earlier marriages but we don't have a date.
You will note that Edward was from the town of Drumshanbo and Frances was from Mahanagh townland which was mistranscribed as Makanagh.
Date of Marriage:05-Jan-1854
Parish / District:DRUMSHANBO CHURCH OF IRELAND
Husband EdwardDecourcy Address Drumshanbo
Wife FrancesStuartAddress: Makanagh
I also looked at the 1857 Griffiths Valuation head of household listing for Kiltoghert civil parish and there were no de Courcy records but I did see an Edward Stewart in Mahanagh townland and possibly he was the father of Frances.
Let me know if you have any questions.