Final answer:
The provided references don't specify the exact percentage of marriages between cousins; however, they explore the evolution of family structures and the variation in laws concerning cousin marriages across the United States.
Step-by-step explanation:
While the original question about the percentage of marriages between 1st and 2nd cousins is not directly answered by the provided references, related sociological insights can be discussed. The incest taboo, as theorized by French anthropologist Claude Lévi-Strauss, creates a distinction between those with whom one has family ties and those with whom one can establish marital ties. Laws regarding cousin marriage vary across states in the United States. Moreover, household structures have evolved, with only 66 percent of children living in households with two married parents, demonstrating a shift from the traditional nuclear family. Another aspect is the demographic data on marriage and divorce rates, indicating that not all first marriages succeed, with some ending in divorce and leading to a blend of family structures.
The closest relevant statistic from the provided data is that about 15 percent of all married couples involve one partner who is in their second marriage while the other partner is in their first marriage, and about 9 percent of married couples are both in their second marriage. This could, in some cases, include marriages between second cousins if not legally prohibited, but there is no specific percentage given for cousin marriages.