My GGGG grandmother Margaret BARRY was born probably around 1765. She married Samuel LAIRD sometime before 1787 (when my GGG grandfather John Laird was born. One of John's siblings was named Barry Laird.)
The family lived in Kilcoo. Samuel Laird (Margaret Barry's husband) was listed in the 1803 Agricultural Census of Down, along with Michael BARRY, John BARRY, William BARRY and Thomas BARRY. One of those four latter men could be Garrett's parents (or my Margaret's parents, or her brothers).
I think Margaret had two brothers, William and James Barry, who were both born in the early 1760's according to what I've found.
Susan Rogers
Grass Valley, California