The remarkable discovery was made by 12-year-old BridgeAnne d’Avignon, of Salinas, California, who created a ground-breaking family tree that connected 42 of 43 U.S. presidents to one common, and rather unexpected, ancestor: King John of England.he only former commander-in-chief not linked to King John is the eighth president, Martin Van Buren, who had Dutch roots. The teen also found out that she is the 18th cousin of President Obama.