Francis Scott Key is F. Scott Fitzgerald's second cousin thrice removed!

F. Scott Fitzgerald
 

→

Edward Fitzgerald
his father

→

Cecelia Fitzgerald
his mother

→

Eliza Scott
her mother

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Philip Key
her father

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John Key, M.D.
his father

→

Francis Key
his brother

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Capt. John Ross Key (Continental Army)
his son

→

Francis Scott Key
his son