In 1534, Henry VIII's Reformation Parliament ratified a bill called An Act Concerning the King's Succession, and it became law that year. It was a landmark piece of legislation, being the first (and by no means the last) of Henry's attempts to sequence his heirs by statute, and its principal jobs were thus to legitimize Henry's recent marriage to Anne Boleyn and to place their offspring foremost in the line of succession to the English throne. But in achieving these ends, the Act did other things as well. First, it declared Henry's long-standing marriage to Catherine of Aragon -- "being before the lawful Wife to Prince Arthur, your elder brother" ( Statutes at Large, 25 Henry VIII c. 22) -- invalid because incestuous; then it extended the principle behind this declaration, making it apply to Henry's subjects and kingdom in a sustained, highly specific manner.
Since many inconveniencies have fallen, as well within this Realm as in other by reason of marrying within the Degrees of Marriage prohibited by God's Laws, that is to say, the Son to marry the Mother, or the Stepmother, the Brother the Sister, the Father his Son's Daughter or Daughter's Daughter, or the Son to marry the Daughter of his Father procreate and born by his Stepmother, or the Son to marry his Aunt, being his Father's or Mother's Sister, or to marry his Uncle's Wife, or the Father to marry his Son's Wife, or the Brother to marry his Brother's Wife, or any Man to marry his Wife's Daughter, or his Wife's Son's Daughter, or his Wife's Daughter's Daughter, or his Wife's Sister; which Marriages...be plainly prohibited and detested by the Laws of God...Be it therefore enacted..., That no Person or Persons, Subjects or Residents of this Realm...shall from henceforth marry within the said Degrees afore rehearsed. ( Statutes at Large, 25 Henry VIII c. 22)
Henry's Parliament worked hard -- presumably under the king's direction -- to make this passage sound as much like the Bible as possible. Nor was the labor wasted; the ponderous rehearsal of forbidden marital unions is closely modeled on similar texts in Leviticus (chapters 18 and 20), where the male reader is enjoined to avoid sex or marriage with his mother,