The House of La Rochefoucauld is counted as one of the oldest in France and has maintained a close contact with power through the ages. From being Lords to Comtes and finally in 1622, the family achieved the ultimate honour of being awarded the title of Duc which came with a peerage.
The House came dangerously close to extinction in 1721 when the last son of Alexandre de La Rochefoucauld died. Due to the law in France at the time females could neither inherit a dukedom nor bestow it on their own sons. In an attempt to avoid the extinction of his House, Alexandre decided to proceed with a case of serious intermarriage.
He suggested marrying his daughter Marie-Louise-Élisabeth to the last of his own brothers - her uncle, that is. "Sadly", she died before the wedding could take place.
In a desperate attempt to survive Alexandre appealed to the King who agreed that the title of Duc could continue with Alexandre's surviving daughter's offspring on one condition: she had to marry a member of her own House. Consequently, she married her first-cousin and the House survived.
Duc de Doudeauville