Yes, the shipping and railroad tycoon Cornelius "Commodore" Vanderbilt married his first cousin, Sophia Johnson, on December 19, 1813. Sophia was the daughter of Cornelius's aunt, Elizabeth Johnson. The couple had a very long marriage that lasted over 50 years until Sophia's death in 1868. Together, they had 13 children, forming the foundation of the prominent Vanderbilt family dynasty. While marriage between first cousins is largely stigmatized today, it was relatively common and legally accepted among prominent American families in the early 19th century as a way to consolidate wealth and maintain social standing. After Sophia passed away, the Commodore married another distant cousin, Frank Armstrong Crawford, who was 43 years his junior. It was Frank who famously encouraged him to donate the $1 million that founded Vanderbilt University in Nashville, Tennessee, late in his life, marking one of his few major philanthropic acts before his death in 1877.