consanguinity

consanguinity

[kon-sang-gwin-i-tee]
consanguinity, state of being related by blood or descended from a common ancestor. This article focuses on legal usage of the term as it relates to the laws of marriage, descent, and inheritance; for its broader anthropological implications, see incest. Consanguinity is to be distinguished from affinity, which is the relation of a person, through marriage, to the consanguineous relatives of a spouse. Marriage between persons in lineal consanguinity (persons in the direct line of descent, such as father and daughter) and between brothers and sisters is void under common law, church law, and statute. Whether or not marriages between persons of collateral consanguinity (those having a common ancestor but not related in direct line of descent) are prohibited as incestuous depends on statutory provision and judicial interpretation. In more than half the states of the United States, marriage between first cousins is prohibited by law, and the Roman Catholic Church and the Orthodox Eastern Church have strict rules on consanguinity as an impediment to marriage. Statutes in the United States discard affinal relationship as an impediment to marriage. Whether incestuous marriages are void or voidable in the United States depends on local statutes and their interpretation. In the law of descent and inheritance, the concept of consanguinity is most important in the area of intestate succession. Most states award the spouse of a person who dies intestate a certain share of the estate, even though there exists neither lineal nor collateral consanguinity between the spouses.

See B. D. Inglis, Family Law (2d ed., 2 vol., 1968-70).

Kinship characterized by the sharing of common ancestors (derived from the Latin consanguineous, meaning “of common blood”). Kin are of two basic kinds: consanguineous (sharing common ancestors) and affinal (related by marriage). Today consanguinity is a genetic concept that influences the probabilities of specific combinations of characteristics, called genotypes. The probability that two consanguineous individuals will share the same traits depends upon the mode of inheritance (dominant or recessive) and the degree of penetrance or expressivity of the causative gene. Higher rates of mortality and rare diseases and disorders are more common in the offspring of consanguineous unions. While consanguineous marriages of various degrees have been practiced, all societies have incest taboos prohibiting marriage or sexual relations between certain kin.

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Consanguinity ("con#Italian (with) sanguine (blood) -ity") refers to the property of being from the same lineage as another person. In that respect, consanguinity is the quality of being descended from the same ancestor as another person. Consanguinity is an important legal concept in that the laws of many jurisdictions consider consanguinity as a factor in deciding whether two individuals may be married or whether a given person inherits property when a deceased person has not left a will.

The degree of relative consanguinity can be illustrated with a consanguinity table, in which each level of lineal consanguinity (i.e., generation) appears as a row, and individuals with a collaterally-consanguineous relationship share the same row. See, e.g., table of consanguinity

Legal definitions

In regard to family law, generally, consanguinity becomes important in defining who may marry and who may inherit. Some U.S. states forbid cousins to marry. Others are more lenient and only forbid individuals to marry their brothers, sisters, mothers, fathers, aunts and uncles. Some U.S. states also prevent individuals from serving on a jury in which they have a certain degree of consanguinity with the defendant.

Several volumes of Smith's Laws, enacted from 1700 through 1829, contain certain public and private laws of the Province and Commonwealth of Pennsylvania. Several laws with a prescribed punishment against adultery, bigamy, incest and fornication and all combinations of those crimes were enacted in 1705. They are found in volume I of Smith's Laws along with a table of Degrees of consaguinity and affinity

In regard to the law of intestate succession (when a person dies without a will), under the Uniform Probate Code of the United States section 2-103, after a surviving spouse receives his or her share, the descendants (depending on the circumstances this may include children, grandchildren, or great grandchildren, either biological or adopted) receive the remainder of the intestate estate. If there are no children, the decedent's parent(s) receive the remainder of the estate. If there are neither descendants nor parents, the decedent's estate is distributed to descendants of the decedent's parents (again, depending on the circumstances, brothers and sisters, nieces and nephews, grand nieces and nephews and great grand nieces and nephews). If there are no descendants, parents, or descendants of parents, then the deceased's property passes to descendants of the grandparents of the decedent (uncles and aunts, first cousins, or first cousins once, twice, or thrice removed).

The connotations of degree of consanguinity varies by context (e.g., Canon law, Roman law, etc.). Most cultures define a degree of consanguinity within which sexual interrelationships are regarded as incestuous (the "prohibited degree of kinship"). In the Roman Catholic Church, unwittingly marrying a closely-consanguineous blood relative is grounds for an annulment, but dispensations were granted, actually almost routinely (the Catholic Church's ban on marriage within the fourth degree of relationship (first cousins) lasted from 1550 to 1917; before that, the prohibition applied to marriages within the seventh degree of kinship). The general rule was that while fourth cousins could marry without dispensation, those more closely related needed dispensation, with it becoming harder and harder to obtain the closer the couple were related.

Adoption may or may not be considered at law to create such a bond; in most Western societies, adoptive relationships are considered blood relationships for these purposes, but in others, including both Japan and ancient Rome, it was common for a couple with only daughters to adopt a son-in-law, making the marriage one between adoptive siblings.

Among the Christian Habesha highlanders of Ethiopia and Eritrea (the predominantly orthodox Christian Amhara and Tigray-Tigrinya), it is a tradition to be able to recount one's paternal ancestors at least 7 generations away starting from early childhood, because "those with a common patrilineal ancestor less than seven generations away are considered 'brother and sister' and may not marry." The rule is less strict on the mother's side, where the limit is about four generations back, but still determined patrilinearly. This rule does not apply to Muslims or other ethnic groups.

Rates of occurrence

Historically, some European nobles cited a close degree of consanguinity when they required convenient grounds for divorce, especially in contexts where religious doctrine forbade the voluntary dissolution of an unhappy or childless marriage. Conversely, the consanguinity law of succession requires the next monarch to be of the same blood of the previous one; allowing, for example, illegitimate children to inherit. It is estimated that 55% of marriages between Mirpuri (Kashmiri) Pakistani immigrants in the United Kingdom are between first cousins, where "preferential patrilateral parallel cousin marriage" (where a boy marries his father's brother's daughter) is often favored.

Genetic Disorders

The offspring of consanguinous relationships are at greater risk of certain genetic disorders. Autosomal recessive disorders occur in individuals who are homozygous for a particular recessive gene mutation. This means that they carry two copies (alleles) of the same gene. Except in certain rare circumstances (new mutations or uniparental disomy) both parents of an individual with such a disorder will be carriers of the gene. Such carriers are not affected and will not display any signs that they are carriers, and so may be unaware that they carry the mutated gene. As relatives share a proportion of their genes, it is much more likely that related parents will be carriers of an autosomal recessive gene, and therefore their children are at a higher risk of an autosomal recessive disorder. The extent to which the risk increases depends on the degree of genetic relationship between the parents; so for incestuous relationships where the parents share 1/2 of their DNA the risk is great, but for relationships between second cousins where the parents only share 1/32 of their DNA the risk is less (although still greater than the general population).

See also

References

  • Kingston H M, "ABC of Clinical Genetics", Pages 7 & 26-27, 3rd Edition (2002), BMJ Books, London, 0-7279-1627-0

External links

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