Henry Churchyard writes that, “the brief answer is that marrrying one’s first cousin has been legal in England since the 16th-century (when England basically adopted the list of prohibited marriages in the book of Leviticus in the Old Testament, following the break with the Catholic church). Here is a Table of Kindred and Affinity from The Book of Common Prayer, 1769, printed by John Baskerville for the Cambridge University Press.