Dan:
It appears that the Caheragh parish liaison has not responded.
I assume you have returned to the States. The Caheragh RC records start in 1818.
http://registers.nli.ie/parishes/0024
I searched www.irishgenealogy.ie which is a free Irish government site and did not find the marriage record. Likely the marriage occurred before 1818 and possibly Catherine had older siblings. I did find baptismal records for two younger brothers and one sister. See below. The originally lived in Clooncuggr townland but by 1825 were in Maune townland
Let me know if you have any questions.
Roger
Area - CORK & ROSS (RC) , Parish/Church/Congregation - CAHARAGH
Baptism of TIMOTHY SULLIVAN of CLOUCUGGIN on 2 April 1822
NameTIMOTHY SULLIVANDate of BirthN/R N/R N/RAddressCLOUCUGGINFatherJERY SULLIVANMotherMARY REAGAN
Further details in the record
Child DenominationRCSponsor 1DARLY BARNETSponsor 2JOA REAGANRecorded Diocesan AreaCORK & ROSSRecorded Parochial AreaCAHARAGH
Area - CORK & ROSS (RC) , Parish/Church/Congregation - CAHARAGH
Baptism of JEREMIA SULLIVAN of CLONCUGIN on 9 November 1823
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NameJEREMIA SULLIVANDate of BirthN/R N/R N/RAddressCLONCUGINFatherCONLS SULLIVANMotherNORY REAGAN
Further details in the record
Child DenominationRCSponsor 1JEREMIA REAGANSponsor 2JULIA SHEARecorded Diocesan AreaCORK & ROSSRecorded Parochial AreaCAHARAGH
Area - CORK & ROSS (RC) , Parish/Church/Congregation - CAHARAGH
Baptism of MARY SULLIVAN of MANE on 4 March 1825
NameMARY SULLIVANDate of BirthN/R N/R N/RAddressMANEFatherJERRY SULLIVANMotherMARY REAGAN
Further details in the record
Child DenominationRCSponsor 1NICHLS DRISCOLLSponsor 2MARGT REAGANRecorded Diocesan AreaCORK & ROSSRecorded Parochial AreaCAHARAGH