If you use the Advance Search for children of Thomas & Ann KNIGHT in Newent, you will find

Edward had at least three siblings: William 1769, Richard 1778 and Ann 1765.

Looking back at the Marriage of Edward KNIGHT to Anna PLAISTER, one witness was Ann KEYCE

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You will find on FOD records - a Marriage at Newent - 7 October 1781

Ann KNIGHT, Spinster - residence Newent married Joseph KEYCE