If Blaesing was, in fact, President Harding's daughter, then, between the 2000 death of John Coolidge and her own death, she was the oldest living child of a President, and between the 1995 death of Francis Cleveland and her own death, Harding was the earliest President still to have a living child.
His earliest American ancestor, John Coolidge, emigrated from Cottenham, Cambridgeshire, England, around 1630 and settled in Watertown, Massachusetts.
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Otherwise, this distinction belonged to Coolidge from 1995 to John Coolidge's death in 2000 and then to Harry S. Truman until 2008, when his daughter Margaret Truman died.