From the Laws of the Presbyters of Northumbria, in What Year Indeed They Were Published Is Uncertain, But They Are Placed by the Collectors of Councils Toward the End of the Tenth Century

Law LII. Let no one contract marriage in his own cognation, namely within the fourth degree or little knee, nor with his co-sponsor at the sacred font.

The former part rather savors of an earlier age. Compare the law of King Canute below.

Law LIV. If anyone has dismissed his own wife living in legitimate matrimony and has illegitimately led another, let him lack the mercy of God, unless he has amended. But let each one justly hold his own marriage as long as the wife shall have lived, unless perhaps it has happened that by the counsel of the Bishop they are separated, so that afterward they live divided in chastity.

While the wife is living, no other conjunction is permitted, even if she has been dismissed.