<P> A recent research study of 70 nations has found a statistically significant negative correlation between consanguineous kinship networks and democracy . The authors note that other factors, such as restricted genetic conditions, may also explain this relationship . This follows a 2003 Steve Sailer essay published for The American Conservative, where he claimed that high rates of cousin marriage play an important role in discouraging political democracy . Sailer believes that because families practicing cousin marriage are more related to one another than otherwise, their feelings of family loyalty tend to be unusually intense, fostering nepotism . </P> <P> Cousins are not included in the lists of prohibited relatives provided in the Bible, specifically in the books of Leviticus and Deuteronomy . The Old Testament also contains several examples of married cousins . Two of the most famous are prominent in Genesis . Rebekah was married to Isaac, her first cousin once removed (Genesis 24: 12--15). Also, Rachel and Leah were both cousins of Isaac's son Jacob . Jacob loved Rachel and worked seven years for her father Laban in return for permission to marry (Genesis 28--29). Jacob's brother Esau also married his cousin Mahalath, daughter of Ishmael . According to many English Bible translations, a fourth example is the five daughters of Zelophehad, who married the "sons of their father's brothers" in the later period of Moses, although other translations merely say "relatives". (For example, the Catholic RSV - CE and NAB differ in Numbers 36: 10--12 .) During the apportionment of Israel following the journey out of Egypt, Caleb gives his daughter Achsah to his brother's son Othniel according to the NAB (Joshua 15: 17), though the Jewish Talmud argues Othniel was simply Caleb's brother (Sotah 11b). The daughters of Eleazer also married the sons of Eleazer's brother Kish in the still later time of David (1 Chronicles 23: 22). King Rehoboam and his wives Maacah and Mahalath were grandchildren of David (2 Chronicles 11: 20). Finally, Tobias in the book of Tobit has a right to marry Sarah because he is her nearest kinsman (Tobit 7: 10), though the exact degree of their cousinship is not clear . </P> <P> In Roman Catholicism, all marriages more distant than first - cousin marriages are allowed, and first - cousin marriages can be contracted with a dispensation . This was not always the case, however: the Catholic Church has gone through several phases in kinship prohibitions . At the dawn of Christianity in Roman times, marriages between first cousins were allowed . For example, Emperor Constantine, the first Christian Roman Emperor, married his children to the children of his half - brother . First and second cousin marriages were then banned at the Council of Agde in AD 506, though dispensations sometimes continued to be granted . By the 11th century, with the adoption of the so - called canon - law method of computing consanguinity, these proscriptions had been extended even to sixth cousins, including by marriage . But due to the many resulting difficulties in reckoning who was related to whom, they were relaxed back to third cousins at the Fourth Lateran Council in AD 1215 . Pope Benedict XV reduced this to second cousins in 1917, and finally, the current law was enacted in 1983 . In Catholicism, close relatives who have married unwittingly without a dispensation can receive an annulment . </P> <P> There are several explanations for the rise of Catholic cousin marriage prohibitions after the fall of Rome . One explanation is increasing Germanic influence on church policy . G.E. Howard states, "During the period preceding the Teutonic invasion, speaking broadly, the church adhered to Roman law and custom; thereafter those of the Germans...were accepted ." On the other hand, it has also been argued that the bans were a reaction against local Germanic customs of kindred marriage . At least one Frankish King, Pepin the Short, apparently viewed close kin marriages among nobles as a threat to his power . Whatever the reasons, written justifications for such bans had been advanced by St. Augustine by the fifth century . "It is very reasonable and just", he wrote, "that one man should not himself sustain many relationships, but that various relationships should be distributed among several, and thus serve to bind together the greatest number in the same social interests". Taking a contrary view, Protestants writing after the Reformation tended to see the prohibitions and the dispensations needed to circumvent them as part of an undesirable church scheme to accrue wealth, or "lucre". </P>

Can you marry your first cousin in catholic church
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