In the 4th century BCE, the
Soferim (
scribes) declared that there were relationships within which marriage is prohibited, in addition to those forbidden by the Bible. These additional relationships were termed
seconds (Hebrew: ), and included the wives of a man's: • father's half-brother on their mother's side • mother's half-brother on their father's side • grandfather • grandson. The classical rabbis prohibited marriage between a man and any of his
seconds, on the basis that doing so would act as a
safeguard against infringing the Biblical prohibitions; one
Talmudic opinion even arguing that the inclusion of the grandfather's wife and of the grandson's wife, among the
seconds, is based on the Biblical rule against a wife's granddaughter. There was however some debate as to which relationships, other than the four listed above, counted as
seconds; the Talmudic scholars and Rabbinic scholars of the middle age, the
Rishonim, variously included or excluded the following relationships from the
seconds of a man: • grandmother's sister • paternal grandfather's sister • paternal grandfather's brother's wife • wife's great-granddaughter (including great-granddaughter) The extent to which the forbidden relationships extend beyond the
seconds is a matter of dispute, but all the Talmudic scholars agree that marriage to the wife of any male descendant, in the direct male line, was forbidden; as did all of the Jewish scholars of the Middle Ages. – the closer relation of the two. Historically, there are a few examples of marriage between cousins; in 19th century England, the proportion of Jewish marriages occurring between cousins was 3.5 times higher than for the marriages of other religions; in the 19th century
Lorraine the proportion was twice as high as that for Roman Catholics, and 12 times higher than that for Protestants.
In practice Marriages forbidden in the Bible were regarded by the rabbis of the Middle Ages, the
Rishonim as invalid – as if they had never occurred; any children born to such a couple were regarded as
mamzerrim "bastards", On the other hand, those relationships which were prohibited due to qualifying as
seconds, and so forth, were regarded as wicked, but still valid; Thus
Jacob ben Meir deliberately wrecked a wedding, stopping the marriage and spoiling the banquet and celebrations, because the man would have married his father-in-law's wife. They also argued that on occasions when the Bible was read in public, and the reading happened to involve some of the Biblical rules against incest, then the reading must be stopped, if the reader interprets the regulations in a different way to the Talmudic opinions. == Karaite views ==