When plotting your next late Regency or early Victorian romance, you may want to check these handy marriage rules before your lovely young heroine falls in love with the hot son of the brother of her cruel, elderly, late husband and the couple must flee England for the Appalachian Mountains (that’s where I found my husband.)
The following is excerpted from The Female’s Friend, and General Domestic Adviser: Including a Complete Alphabetical Receipt Book. Instructions in Dress Making, &c by Robert Huish and published in 1837.
AFFINITY.—Prohibited degrees of consanguinity or relationship by blood, as well as affinity or relationship by marriage, on the man’s part.
The husband and wife being, he who is related to one by consanguinity, is related to the other by affinity, in the same degree. Marriage in the descending or ascending line, that is, of children with their father, grandfather, mother, grandmother, and so upwards, are prohibited without limit, because they are the cause, immediately or mediately, of such children’s being; and it is directly repugnant to the order of their nature, which hath assigned several duties and offices essential to each, that would thereby be inverted and overthrown. A parent cannot obey his child, and therefore it is unnatural that a parent should be wife to a child.
Further, such absolute prohibitions are necessary, to prevent the incongruity, absurdity, and monstrous enormity of the relations to be begotten:—the son or daughter, for instance, born of the mother and begotten by the son, considered as born of the mother, would be a brother or sister to the father, but as begotten by him would be a son or daughter. It is certain, however, that civilians have not been much employed in annulling incestuous marriages, contracted between men and their grandmothers, or their grandfathers’ wives, —or between women and their grandfathers; but an alliance not very remote from such a one, happened by a man marrying the wife of his great uncle, which was declared not to be within the levitical degrees. The question whether a man can marry his wife’s sister is not finally determined.