Mary Flagg Bemis was born 1771 in Spencer, Worcester County, Massachusetts, United States to Samuel Flagg (1733-1811) and Grace Fiske (1739-1800) . She married John Bemis (1767-1852) 5 July 1796 in Spencer, Worcester County, Massachusetts.
|Offspring of John Bemis and Mary Flagg (1771-)|
|Mary Flagg Bemis (1797-)|
|Samuel Flagg Bemis (1797-1837)||1 March 1797 Paxton, Worcester County, Massachusetts, United States||13 October 1837 Jefferson County, New York, United States||Elizabeth Bigelow (1796-1842)|
|Catherine Flagg Bemis (1798-1878)|