Which President Married His Cousin
John Quincy Adams is the only U.S. president who married a cousin, according to the most recent public records from the White House Historical Association and the National Archives. He married Louisa Catherine Johnson in London on July 26, 1797. Louisa was the daughter of Joshua Johnson, a U.S. merchant and consul, and the niece of John Adams's mother, Susanna Boylston Adams. The marriage linked the Adams family to a transatlantic diplomatic and merchant network during the early republic. White House biography of John Quincy Adams lists the couple and their children.
The relationship between John Quincy Adams and Louisa Catherine Johnson was a second-cousin marriage, meaning they shared great-grandparents. Genealogical research from the Adams Family Papers, held at the Massachusetts Historical Society, traces the Johnson and Adams lines through Susanna Boylston and the Johnson merchant family. The marriage produced four children, including future U.S. Representative and diplomat Charles Francis Adams. Massachusetts Historical Society Adams Family Papers provide primary-source documentation of the family connections.
Historical Context of Presidential Cousin Marriages
In the late 18th and early 19th centuries, cousin marriage was common among elite European and American families, including political dynasties. The practice helped preserve wealth, maintain social standing, and keep alliances within established networks. John Quincy Adams's marriage fits this pattern, alongside other prominent families such as the Roosevelts, who later married cousins in later generations. Forbes overview of cousin marriage history explains the social and economic drivers behind these unions.
The U.S. Constitution does not prohibit marriage between cousins, and federal law defers to state rules on marriage eligibility. Today, cousin marriage remains legal in many U.S. states, though some states restrict or ban first-cousin marriages. The Adams marriage is documented as a second-cousin union, which is legal in all 50 states. National Conference of State Legislatures cousin marriage laws page provides a current state-by-state summary of the legal status.
Other Presidents With Notable Family Connections
Presidential Couples With Distant Family Ties
While John Quincy Adams is the only president who married a cousin, other presidents had family connections through broader kinship networks. Franklin D. Roosevelt and Eleanor Roosevelt were fifth cousins, once removed, sharing common ancestors from the Roosevelt and Delano families. Their marriage is documented in the Roosevelt Presidential Library and Museum holdings. Franklin D. Roosevelt Presidential Library and Museum provides genealogical resources on the Roosevelt family.
Why Cousin Marriages Are Rare Among Modern Presidents
Modern presidential families tend to have more geographically dispersed social networks, and changing social norms have reduced the frequency of cousin marriages in political circles. Public scrutiny and media coverage also make family connections more visible. The Adams precedent remains the only documented case of a U.S. president marrying a cousin, according to the latest biographical data from the White House Historical Association and the Miller Center at the University of Virginia. Miller Center biography of John Quincy Adams includes family background and