Bryan O'BANNON's grandson Bryant O'BANNON 1749-1784 was married to an UNK Elizabeth. He was the son of John O'BANNON and Sarah BARBEE.
I have looked through my many Elizabeth DUNCAN's and have not found one married to Bryan O'BANNON.
Our Joseph DUNCAN c1712-1792 (m UNK Lydia) is thought to be the son of a John DUNCAN b. 1685 Scotland. John's wife is unknown to us. Joseph named his first daughter Lydia Elizabeth DUNCAN, so it is very possible that Joseph's mother was an Elizabeth.As a widow, she would then be Elizabeth DUNCAN in the right generation to m 2) Bryan O'BANNON b 1683.
Do you have any documentation?? This would probably be in Stafford Co., Va.