DNA confirmed people with O surname
- John Aloysius O'Brien ( - 1937)
- Florence O'Brien ( - 1967)
- Cecelia Bernice Veronica O'Brien (1903 - 1996)
- Anna Olfert (ABT 1872 - ABT 1935)
- Isaak Olfert (ABT 1845 - ABT 1890)
- Margaret Frances Olives (28 Feb 1925 - 31 Jan 1988)
- Lila Juanita Olives (ABT 1922 - ABT 1992)
- Robert Lee Olives (10 Aug 1927 - 14 Mar 2017)
- Melba Myrtle Olives (28 Aug 1918 - 31 Dec 1978)
- Rid Thomas Olives (25 Sep 1884 - 26 Jan 1952)
- M Oosterink (1932 - 2015)
- Amie Overby (1812 - ABT 1867)
- Archibald Overby (1796 - ABT 1878)
- Mary Elizabeth Overby (ABT 1830 - 13 Mar 1898)
- Nicholas Overby (ABT 1776 - ABT 1857)
- Caroline Priscilla Overby (ABT 1840 - 10 Mar 1907)