As I understand it, the McGaffin-Kennedy marriage failed... marriage of the younger daughter at Knocknamuckley CoI is new information to me. Thank you for posting this.
That was my assumption when saw earlier that James had remained rather than died. The daughter's marriage is really where I picked up, having been going sideways and forwards with the husband's surname, a distant cousin. Only looked into the McGaffin's when google produced this Rootschat post when I pasted 'Forest Avenue, Amsterdam, Montgomery' into my search bar to see where it was.
Thomas was born Lurgan 19 Jan 1917 but, presumably with work, at some point they moved to Limavady where Thomas died 15 Dec 2001 aged 84 and Anne 6 Feb 2012 aged 91. They had a son William and a daughter May. William married a divorcee Derry district with one daughter then they had another daughter together and lives in Limavady (electoral rolls). May possibly married when in her 60's. Thomas & Annie were interred in Lurgan Cemetery in a double width plot with new headstone & surround, I happened to photograph it on a visit a few years back.
I looked for a death index entry for Annie McGaffin and did not see one when typing earlier, but there is a 50 year online cut-off on deaths [and 100 on births - I have later transcribed data for Thomas' surname only, from unrestricted BMD index searches conducted in the GRONI office in Belfast].
There is a marriage index entry for a Sarah McGaffin to a John Green in Craigavon district 1947 but also another to a Thomas Frank in Banbridge District same year, the Craigavon (Lurgan) the more likely but the districts ajoin.
Searching the Lurgan Mail on Findmypast/British Newspaper Archive, though with expired subscription so limited to the OCR summaries, Anna Mary was at 78 Russell Drive Lurgan 1970 -1980 and must have had another son William McGaffin post return (wife Maureen).
McGAFFIN memories of a dear son and brother, Willie, died May 10, 1976. Always remembered by his loving mother Anna, and sisters, Sadie and Annie. [7 May 1981 Lurgan Mail]
With a bit of alteration (keyphrase Anna Mary instead) 24 September 1981 Lurgan Mail:
McGAFFIN - September 19 1981 at hospital, Anna Mary in her 87th year, late of 78C Russell Drive, Lurgan formerly Kennedy, Bleary. Dearly loved mother of Sadie, Annie and the late Billy McGaffin. Interred in Knocknamuckley.
Knocknamuckley headstones are on Armagh Family History Group
https://www.facebook.com/groups/1102863963062370/media/albums as 439 unindexed photos.