This might be a long shot; My ancestor Randolph (also called Randal/Randle) Blackshear was married to Kathryn Anglin (b. 1790), and they lived in Henry Co. The marriage took place in Putnam Co GA. Maybe it's the same family, and that's where they came from. The marriage record spells her name Caty Aunglin.
Good luck.
Genie