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I searched the subscription site Roots Ireland and did not locate the marriage record or any baptismal records for children of Cornelius and Ann. Cornelius is not listed in the 1850 Griffiths Valuation head of household survey for Co. Limerick which indicates he was not leasing land.
Actual civil death records are available from 1878-1969. From 1864-1877, we only have index records for now but over time the images will be added to www.irishgenalogy.ie The index record for Ann on Roots Ireland indicates she was a labourer's wife, the informant was Cornelius Walsh and they lived in a place called Gurrane which I believe is Garrane in Monasteranenagh civil parish.
Likely the family was living in an area where the RC parish records do not go back to the 1840s. There are at least eight parishes in this category. One possibility is Banogue RC parish which is just to the northwest of Croom parish.
Let me know if you have any questions.