Prohibited Degrees of Affinity

Something else from the pile:

Religious belief, campaigns and causes might also produce tightly knit coteries and a preference for marrying within the circle. The Evangelicals of the Clapham Sect, inspired by William Wilberforce, lived almost as a commune. They mimicked kinship bonds, called each other brother, and bequeathed the idea of intermarriage to succeeding generations. ... Competition for pious daughters was intense. Sisters were in demand too, although this raised problems. When a wife died, her sister was often the preferred replacement, except that canon law forbade marriage with a deceased wife’s sister on the grounds that man and wife were one, so a sister-in-law was a sister, hence marriage would constitute incest. This logic gave rise to one of the great Victorian public debates. To begin with, nobody was quite sure what incest was. In 1847, a Royal Commission was set up to investigate "prohibited degrees of affinity", and for the next six decades the argument raged. The radical John Bright appealed to common sense: on every "natural" ground, he urged, the marriage of first cousins was more objectionable than marriage to a sister-in-law. (On the evidence here there was a good chance the deceased wife’s sister was a first or second cousin anyway.) The Bible gave contradictory guidance. Leviticus seemed to ban sisters-in-law, but then there was Jacob, married to two sisters, Rachel and Leah, who were also his cousins. It was not until 1907 that a Bill was passed permitting a man to marry his deceased wife’s sister (although not until 1949 his divorced wife’s sister). Meanwhile, natural scientists and medical men raised questions about inbreeding, and by the 1920s eugenicists routinely condemned cousin marriage. By then, families had shrunk and the First World War had wiped out a generation of male cousins.

Norma Clarke reviews Adam Kuper's book on the Victorian bourgeoisie's habit of marrying their cousins.