Cousin Marriage – Why? – Why Not?

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Source: Muslim Sunrise, Fall 2015

By Dr. Lutf ur Rehman, Nashville, Tennessee

Marriage between people with a common grandparent or between people who share another relatively recent ancestor is called cousin marriage. Such marriages range from being considered ideal and actively encouraged, to being uncommon but still legal, to be seen as incestuous and legally prohibited. Although now stigmatized in the Western world, they remain relatively common in the Middle East and Southeast Asia, where, in some countries such as Pakistan and Saudi Arabia, they account for over half of all marriages. Worldwide, over one in every ten marriages is between first and second cousins.

All religions and cultures place some restrictions while choosing marriage partners. In the Holy Scriptures of Islām, Judaism and Christianity, there is no prohibition on marrying your first or any cousin. The Old Testament contains several examples of married cousins. Two of the most famous are prominent in Genesis. Isaac was married to Rebekah, his first cousin once removed (Genesis 24:12–15). First and second cousin marriages were then banned at the Council of Agde in AD 506. In the present day Roman Catholicism, all marriages more distant than first-cousin marriages are allowed.

Christianity: 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.”[1] On the other hand it has also been argued that the bans were a reaction against local Germanic customs of kindred marriage.[2] At least one Frankish King, Pepin the Short, apparently viewed close kin marriages among nobles as a threat to his power.[3] 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.”[4] 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.”

Islam: The Qur’an does not state that marriages between first cousins are forbidden. In Sura An-Nisa (4:23–25), Allah mentioned the women who are forbidden for marriage: to quote the Qu’ran, “… Lawful to you are all beyond those mentioned, so that you may seek them with your wealth in honest wedlock…” The list of prohibited women does not include first or any cousin.

Muslims have practiced marriages between first cousins in non-prohibited countries since the time of Muhammad (saw). In a few countries the most common type is between paternal cousins.[5]

Holy Prophet (saw) married two cousins. One was a first cousin, Zaynab bint Jahsh, (ra) who was not only the daughter of one of his father’s sisters but was also divorced from a marriage with Muhammad’s (saw) adopted son, Zayd ibn Haritha (ra). It was the issue of adoption and not cousinship that caused controversy due to the opposition of pre-Islamic Arab norms.[6]

Many of the immediate successors of Muhammad (saw) also took a cousin as one of their wives. Umar (ra) married his cousin Atikah bint Zayd ibn Amr ibn Nifayl,[7] while Ali (ra) married Fatimah (ra), the daughter of his paternal first cousin Muhammad (saw) and hence his first cousin once removed.[8]

Even though most Muslims practice cousin marriage now, two of the Sunni Muslim madhhabs (schools, four in total) like Shafi’i (about 33% of Sunni Muslims) and Hanbali consider it Makruh (disliked), and there are three Ahadith that prefer marriage outside of the family but all of them are considered ḍaʿīf (weak), even though some scholars like Ibn Qudamah and Al-Ghazali prefer marriage outside the family, because if a divorce happened between the couple the family bond will be weakened or broken.

Hinduism: Hindu Marriage Act bans all kinds of first cousin marriage, but permits them when allowed by local custom. North Indian Hindus treat all kinds of first cousin marriage as incest, but same is not the case with south Indian Hindus. Major Dharmaśāstra like Yājñavalkya Smṛti and Manusmṛti also ban cousin marriage. In Hinduism marriage within the same gotra is prohibited. A gotra is the group of descendants of a sage who lived in the remote past. Two persons in the same gotra cannot marry even if they come from different linguistic areas. However, same-gotra marriages have been legal under Indian civil law since the Hindu Marriage Act of 1955. Additionally, marriages within certain degrees of consanguinity are considered sapinda and banned in Hinduism. Hindu lawgivers differ in the definition of sapinda: at one extreme, according to some sources marriages are prohibited within seven generations on the father’s side and five on the mother’s side. In contrast, other sources allow cross cousins to marry, including first cross cousins. The Hindu Marriage Act prohibits marriage for five generations on the father’s side and three on the mother’s side, but allows cross-cousin marriage where it is permitted by custom.[9]

In the 18th and 19th Centuries, Hindu Kurmis of Chunar and Jaunpur are known to have been influenced by their Muslim neighbors and taken up extensively the custom of cousin marriage.[10]

In the Mahabharata, one of the two great Hindu Epics, Arjuna took as his fourth wife his first and cross cousin Subhadra, the sister of Krishna.

Buddhism does not proscribe any specific sexual practices, only ruling out “sexual misconduct” in the Five Precepts. Zoroastrianism allows cousin marriages. Sikhism largely follows the pattern of ban on the same clan marriages.

Social Aspects: It appears that in most societies cousin marriage is more common among those of low socioeconomic status, among the illiterate and uneducated, and in rural areas.[11] This may be due in part to the token or significantly reduced dowries and bridewealths that exist in such marriages and also the much smaller pool of viable marriage candidates in rural areas. But some societies also report a high prevalence among land-owning families and the ruling elite: here the relevant consideration is thought to be keeping the family estate intact over generations.[12]

Anthropologists Robert Murphy and Leonard Kasdan describe preferential parallel cousin marriage as leading to social fission, in the sense that “feud and fission are not at all dysfunctional factors but are necessary to the persistence and viability of Bedoin society.” Their thesis is the converse of Fredrik Barth’s, who describes the fission as leading to the cousin marriage.”[13] Per Murphy and Kasdan, the Arab system of parallel cousin marriage works against the creation of homogenous “bounded” and “corporate” kin groups and instead creates arrangements where every person is related by blood to a wide variety of people, with the degree of relationship falling off gradually as opposed to suddenly. Instead of corporate units, Arab society is described as having “agnatic sections,” a kind of repeating fractal structure in which authority is normally weak at all levels but capable of being activated at the required level in times of war. They relate this to an old Arab proverb: “Myself against my brother; my brother and I against my cousin; my cousin, my brother and I against the outsider.” In such a society even the presence of a limited amount of cross-cousin marriage will not break the isolation of the kin group, for first cross cousins often end up being second parallel cousins.” Instead of organizing horizontally through affinal ties, when large scale organization is necessary it is accomplished vertically, by reckoning distance from shared ancestors. This practice is said to possess advantages such as resilience and adaptability in the face of adversity.

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.[14] 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.[15]

Biology and Science: Cousin marriage has genetic aspects that do not arise in the case of other marriage-related political and social issues like interracial marriage. This is because married couples that possess higher than normal consanguinity, shared identical DNA and genetic material, have an increased chance of sharing genes for recessive traits. The percentage of consanguinity between any two individuals decreases fourfold as the most recent common ancestor recedes one generation. First cousins have four times the consanguinity of second cousins, while first cousins once removed have half that of first cousins. Double first cousins have twice that of first cousins and are as related as half-siblings.

In April 2002, the Journal of Genetic Counseling released a report which estimated the average risk of birth defects in a child born of first cousins at 1.7–2.8% over an average base risk for non-cousin couples of 3%, or about the same as that of any woman over age 40.[16] In terms of mortality, a 1994 study found a mean excess pre-reproductive mortality rate of 4.4%,[17] while another study published in 2009 suggests the rate may be closer to 3.5%.[18] Put differently, first-cousin marriage entails a similar increased risk of birth defects and mortality as a woman faces when she gives birth at age 41 rather than at 30. Critics argue that banning first-cousin marriages would make as much sense as trying to ban childbearing by older women. (doctors regularly advise women to have children at younger ages and avoid pregnancy after 40 when the risk of birth defects is high)

In the year 2014, two studies from North India (Jammu and Kashmir), reported in PLoS ONE and American Journal of Human Biology providing the evidence for inbreeding depression on cognitive behavior[19] and physical traits (height, weight and body mass index).

Although isolated cousin marriages may pose little risk, repeated consanguineous marriages within a group are more problematic. After repeated generations of cousin marriage the actual genetic relationship between two people is closer than the most immediate relationship would suggest. In Pakistan, where there has been cousin marriage for generations and the current rate may exceed 50%, one study estimated infant mortality at 12.7 percent for married double first cousins, 7.9 percent for first cousins, 9.2 percent for first cousins once removed/double second cousins, 6.9 percent for second cousins, and 5.1 percent among non-consanguineous progeny. Among double first cousin progeny, 41.2 percent of pre reproductive deaths were associated with the expression of detrimental recessive genes, with equivalent values of 26.0, 14.9, and 8.1 percent for first cousins, first cousins once removed/double second cousins, and second cousins respectively.[20]

Even in the absence of preferential consanguinity, alleles that are rare in large populations can randomly increase to high frequency in small groups within a few generations due to the founder effect and accelerated genetic drift in a breeding pool of restricted size. For example, because the entire Amish population is descended from only a few hundred 18th-century German-Swiss settlers, the average coefficient of inbreeding between two random Amish is higher than between two non-Amish second cousins.[21] First-cousin marriage is taboo among Amish but they still suffer from several rare genetic disorders. In Ohio’s Geauga County, Amish make up only about 10 percent of the population but represent half the special needs cases. In the case of one debilitating seizure disorder, the worldwide total of 12 cases, exclusively involve Amish sufferers. Similar disorders have been found in the Fundamentalist Church of Jesus Christ of Latter-Day Saints, who do allow first-cousin marriage and of whom 75 to 80 percent are related to two 1830s founders.[22]

Studies into the effect of cousin marriage on polygenic traits and complex diseases of adulthood have often yielded contradictory results due to the rudimentary sampling strategies used. Both positive and negative associations have been reported for breast cancer and heart disease. Long-term studies conducted on the Dalmatian islands in the Adriatic Sea have indicated a increased association between inbreeding and a very wide range of common adulthood disorders, including hypertension, coronary heart disease, stroke, cancer, uni/bipolar depression, asthma, gout, peptic ulcer, and osteoporosis. However, these results may principally reflect village endogamy rather than consanguinity per se. Endogamy is marrying within a group and in this case the group was a village. The marital patterns of the Amish are also an example of endogamy.

A BBC report discussed Pakistanis in Britain, 55% of whom marry a first cousin.[23] Given the high rate of such marriages, many children come from repeat generations of first-cousin marriages. The report states that these children are 13 times more likely than the general population to produce children with genetic disorders, and one in ten children of first-cousin marriages in Birmingham either dies in infancy or develops a serious disability. The BBC also states that Pakistani-Britons, who account for some 3% of all births in the UK, produce “just under a third” of all British children with genetic illnesses. Published studies show that mean perinatal mortality in the Pakistani community of 15.7 per thousand significantly exceeds that in the indigenous population and all other ethnic groups in Britain. Congenital anomalies account for 41 percent of all British Pakistani infant deaths.[24]

Conclusion: The risk of genetic birth defects and other illnesses may be increased two fold in the marriage of two first cousins. (from a base line of about 3% to 6%). This risk decreases as the distance between the two partners in marriage increases. Second and third cousins are less risky. Inbreeding for generations increases the risk even among the distant relatives and most certainly among closer cousins much more than an occasional first cousin marriage.

There may be a higher social incentive for cousin marriage, such as better family support, less risk of marriage breakdown, preservation of family wealth, land or political power etc. In some circumstances there may be necessity due to a small social or religious group and less choice of marital partners. With these considerations, cousin marriage can still make sense for some, while others will try to avoid it. This may be the reason why none of the scriptures has outright banned cousin marriage keeping in view the varying circumstances of the people.

Even as prohibition of cousin marriage is not prescribed in the scriptures of any religion and many founders and holy men of these religions married their first or second cousins, later followers placed restrictions on such marriages. The permissions in the scriptures are not meant to be orders. These are permissions to address certain special circumstances.


[1] Howard, G.E. (1904). A History of Matrimonial Institutions 1. Chicago: University of Chicago Press. p. 291

[2] Goody, Jack (1983). The Development of the Family and Marriage in Europe. Cambridge: Cambridge University Press. p. 59

[3] Gies, Joseph; Gies, Frances (1983). Marriage and the Family in the Middle Ages. New York: Harper and Row

[4] Ottenheimer, Martin (1996). “Chapter 5”. Forbidden Relatives: The American Myth of Cousin Marriage. University of Illinois.

[5] Andrey Korotayev. “Parallel-Cousin (FBD) Marriage, Islamization, and Arabization.” Ethnology, Vol. 39, No. 4, pp. 395–407

[6] Watt, Muhammad at Medina, p. 330

[7] al-Bidayah wa al-Nihayah 6/352 by ibn Kathir

[8] Nasr, Seyyed Hossein. “Ali”. Encyclopædia Britannica Online. Encycloedia Britannica, Inc. Retrieved 2007-10-12

[9] “Hindu Marriage Act, 1955”. Government of Punjab: Department of Revenue, Rehabilitation and Disaster Management.

[10] Christopher Bayly, Townsmen and Bazaars: North Indian Society in the Age of British Expansion, 1770, p. 49

[11] Bittles, Alan H. (May 2001). A Background Summary of Consanguineous Marriage  (Technical report). Edith Cowan University.

[12] Bittles 1994, p. 567

[13] Murphy, Robert F.; Kasdan, Leonard (Feb 1959). “The Structure of Parallel Cousin Marriage”. American Anthropologist (Blackwell Publishing) 61 (1): 17–29.

[14] Woodley, Michael A.; Edward Bell (2013). “Consanguinity as a Major Predictor of Levels of Democracy: A Study of 70 Nations”. Journal of Cross-Cultural Psychology 44 (2): 263–280

[15] Sailer, Steve (Jan 2003). McConnell, Scott, ed. “Cousin Marriage Conundrum”. The American Conservative: 20–22

[16] Connor, Steve (2008-12-24). “There’s nothing wrong with cousins getting married, scientists say”. The Independent (London).

[17] Bittles, A.H.; Neel, J.V. (1994). “The costs of human inbreeding and their implications for variation at the DNA level”. Nature Genetics 8 (2): 117–121

[18] Kershaw, Sarah (November 26, 2009). “Shaking Off the Shame”. The New York Times.

[19] Fareed M, Afzal M. (2014) Estimating the inbreeding depression on cognitive behavior: A population based study of child cohort. PLoS ONE. 9(10):e109585.

[20] Bittles, Alan H. (September 1994). “The Role and Significance of Consanguinity as a Demographic Variable”. Population and Development Review (Population Council) 20 (3): 561–584.

[21] Hostetler, John Andrew (1993). Amish Society. Baltimore: Johns Hopkins University Press. ISBN 978-0-8018-4442-3.

[22] Dougherty, John (Dec 29, 2005). “Forbidden Fruit”. Phoenix New Times.

[23] Rowlatt, J, (2005) “The risks of cousin marriage”, BBC Newsnight.

[24] Bittles, Alan H. (September 1994). “The Role and Significance of Consanguinity as a Demographic Variable”. Population and Development Review (Population Council) 20 (3): 561–584.

Reference in the Muslim Sunrise

Suggested reading

The tragic truth about cousin marriages: They can cause a litany of genetic illnesses and they’re a key factor in the deaths of two children a week in Britain, so why is it taboo to talk about them, asks SUE REID


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