Until the beginning of the 20th century, incest was well seen in their culture (since they were obsessed with having pure Basque blood), there is an event in the history of the Basque region called "the great Basque resistance", basically this could be Summarize that the Basque tribes hid from the Romans in caves in remote areas and reproduced among members of the same tribe, obviously causing incest. This blood purity issue is so ingrained in their culture that currently Basque parents ask that their boyfriends of their children have "eight Basque surnames" (these surnames belonging to their ancestors).