Not researching this family but there are resources you can find:

www.askaboutireland.ie Griffith Valuation

Thomas Prentice, Parish of Drumcree, DerryKerran Townland

1)William & 2)Hannah Cumming, same parish of Drumcree and 2)Drumcree Townland, and 1)Townland Corcrain

There is also a Thomas Prentice owning land - IN FEE -very rare - in the Parish of Grange, Mullnure.

RC or Protestant? There are Protestant marriages from 1845-1862 before civil registration in 1864.

There are two bmd websites in Armagh

www.emeraldancestors.com - free search - fee paying for records

An Irish History Foundation, fee paying even to search but
a really good source. There records for the area you are looking at are:
RC Drumcree(Portadown)baptism/births 1844-1900, 1863-1900 marriages same, deaths 1863-1900
Eglish 1862-1900 birth and marriage deaths 1877-1900

Church of Ireland
Has no birth records at all before civil registration 1864
marriages all dated the same 1845-1921

There are 11 Cummings in the british telephone book for armagh and although none live in Eglish, Kildarton then you probably should write to everyone. A map might be helpful.

There is only 1 Prentice in Armagh in Killylea and there was 1 Cummings in Killylea.

If Joseph had his own land (not owned) he would be in
the Tithe Applotments (1820-1839) just online other than Ancestry.

www.genealogy.nationalarchives.ie

There are early directories Pigots 1824 & Slaters 1846 on the website you might find them there but farmers don't show in directoris till at least 1881 & 1894.
www.failteromhat.com

Annette Code