Consanguinity refers to the property of being from the same kinship
Kinship is a relationship between any entities that share a genealogical origin, through either biological, cultural, or historical descent. And descent groups, lineages, etc. are treated in their own subsections....

 as another person. In that respect, consanguinity is the quality of being descended from the same ancestor
An ancestor is a parent or the parent of an ancestor ....

 as another person. Consanguinity is an important legal concept in that the law
Law is a system of rules and guidelines which are enforced through social institutions to govern behavior, wherever possible. It shapes politics, economics and society in numerous ways and serves as a social mediator of relations between people. Contract law regulates everything from buying a bus...

s 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 kinship terminology, a cousin is a relative with whom one shares one or more common ancestors. The term is rarely used when referring to a relative in one's immediate family where there is a more specific term . The term "blood relative" can be used synonymously and establishes the existence of...

, in which each level of lineal consanguinity (i.e., generation
Generation , also known as procreation in biological sciences, is the act of producing offspring....

) appears as a row, and individuals with a collaterally consanguineous relationship share the same row. See, e.g., table of consanguinity. The Knot System is a numerical notation that defines consanguinity. It is exact.

Legal definitions

Issues of consanguinity arise in several aspects of the law. It is directly relevant in determining whether a couple can marry. These are linked to a jurisdiction's definition of incest
Incest is sexual intercourse between close relatives that is usually illegal in the jurisdiction where it takes place and/or is conventionally considered a taboo. The term may apply to sexual activities between: individuals of close "blood relationship"; members of the same household; step...

, so that couples in an incestuous relationship will not be permitted to marry. Some United States jurisdictions forbid first-cousins to marry, while others limit the prohibition to brothers, sisters, mothers, fathers, aunts and uncles.

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.

Consanguinity is also relevant in issues of inheritance
Inheritance is the practice of passing on property, titles, debts, rights and obligations upon the death of an individual. It has long played an important role in human societies...

. In regard to the law of intestate succession
Intestacy is the condition of the estate of a person who dies owning property greater than the sum of their enforceable debts and funeral expenses without having made a valid will or other binding declaration; alternatively where such a will or declaration has been made, but only applies to part of...

 (when a person dies without a will), under the Uniform Probate Code
Uniform Probate Code
The Uniform Probate Code is a uniform act drafted by National Conference of Commissioners on Uniform State Laws governing inheritance and the decedents' estates in the United States...

 of the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 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).

Also, some jurisdictions prohibit individuals from serving on a jury
A jury is a sworn body of people convened to render an impartial verdict officially submitted to them by a court, or to set a penalty or judgment. Modern juries tend to be found in courts to ascertain the guilt, or lack thereof, in a crime. In Anglophone jurisdictions, the verdict may be guilty,...

 in which they have a certain degree of consanguinity with the defendant
A defendant or defender is any party who is required to answer the complaint of a plaintiff or pursuer in a civil lawsuit before a court, or any party who has been formally charged or accused of violating a criminal statute...


The connotations of degree of consanguinity varies by context (e.g., Canon law
Canon law (Catholic Church)
The canon law of the Catholic Church, is a fully developed legal system, with all the necessary elements: courts, lawyers, judges, a fully articulated legal code and principles of legal interpretation. It lacks the necessary binding force present in most modern day legal systems. The academic...

, Roman law, etc.). Most cultures define a degree of consanguinity within which sexual interrelationships are regarded as incest
Incest is sexual intercourse between close relatives that is usually illegal in the jurisdiction where it takes place and/or is conventionally considered a taboo. The term may apply to sexual activities between: individuals of close "blood relationship"; members of the same household; step...

uous (the "prohibited degree of kinship
Prohibited degree of kinship
In law, a prohibited degree of kinship refers to a degree of consanguinity between persons that results in certain actions between them becoming illegal. Two major examples of prohibited degrees are found in incest and nepotism. Incest is a taboo across all cultures worldwide, but which specific...


In the Roman Catholic Church
Roman Catholic Church
The Catholic Church, also known as the Roman Catholic Church, is the world's largest Christian church, with over a billion members. Led by the Pope, it defines its mission as spreading the gospel of Jesus Christ, administering the sacraments and exercising charity...

, unwittingly marrying a closely consanguineous blood relative is grounds for an annulment
Annulment is a legal procedure for declaring a marriage null and void. Unlike divorce, it is usually retroactive, meaning that an annulled marriage is considered to be invalid from the beginning almost as if it had never taken place...

, but dispensation
Dispensation (Catholic Church)
In the canon law of the Roman Catholic Church, a dispensation is the suspension by competent authority of general rules of law in particular cases...

s were granted, actually almost routinely (the Canon law of the Catholic Church banned marriages within the fourth degree of relationship [third cousins] from at least the year 1215). In the Canon Law system (as well as in the common law system), the degree of relationship is determined by counting the number of steps counted between each party to the common ancestor and taking the higher number of the two. 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 is a process whereby a person assumes the parenting for another and, in so doing, permanently transfers all rights and responsibilities from the original parent or parents...

 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
Ethiopia , officially known as the Federal Democratic Republic of Ethiopia, is a country located in the Horn of Africa. It is the second-most populous nation in Africa, with over 82 million inhabitants, and the tenth-largest by area, occupying 1,100,000 km2...

 and Eritrea
Eritrea , officially the State of Eritrea, is a country in the Horn of Africa. Eritrea derives it's name from the Greek word Erethria, meaning 'red land'. The capital is Asmara. It is bordered by Sudan in the west, Ethiopia in the south, and Djibouti in the southeast...

 (the predominantly orthodox Christian Amhara
Amhara people
Amhara are a highland people inhabiting the Northwestern highlands of Ethiopia. Numbering about 19.8 million people, they comprise 26% of the country's population, according to the 2007 national census...

 and Tigray-Tigrinya
Tigray-Tigrinya people
Tigray-Tigrinya are an ethnic group who live in the southern, central and northern parts of Eritrea and the northern highlands of Ethiopia's Tigray province. They also live in Ethiopia's former provinces of Begemder and Wollo, which are today mostly part of Amhara Region, though a few regions...

), 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.

Genetic definitions

The percentage of consanguinity between any two individuals decreases fourfold as the most recent common ancestor
Most recent common ancestor
In genetics, the most recent common ancestor of any set of organisms is the most recent individual from which all organisms in the group are directly descended...

 recedes one generation. Consanguinity means the amount of shared (identical) DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

, the genetic
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....

 material. For example, first cousins have four times the consanguinity of second cousins. First cousins once removed have half the shared DNA as full first cousins. Half-fourth cousins sometimes cannot be detected at the DNA level. Finally, double first cousins share twice the consanguinity as first cousins and are as related as half-siblings.

As a working definition, unions contracted between persons biologically related as second cousins or closer (F ≥ 0.0156) are categorized as consanguineous. This arbitrary limit has been chosen because the genetic influence in marriages between couples related to a lesser degree would usually be expected to differ only slightly from that observed in the general population. Globally, the most common form of consanguineous union contracted is between first cousins, in which the spouses share 1/8 of their genes inherited from a common ancestor, and so their progeny are homozygous
Zygosity refers to the similarity of alleles for a trait in an organism. If both alleles are the same, the organism is homozygous for the trait. If both alleles are different, the organism is heterozygous for that trait...

 (or more correctly autozygous) at 1/16 of all loci. Conventionally this is expressed as the coefficient of inbreeding (F) and for first cousin offspring, F = 0.0625. That is, the progeny are predicted to have inherited identical gene copies from each parent at 6.25% of all gene loci, over and above the baseline level of homozygosity in the general population. In some large human populations genetically closer marriages also are favoured, in particular uncle-niece and double first cousin unions where the level of homozygosity in the progeny is equivalent to 0.125.

Gotra system

The Ancient Indian seers developed an interesting practice of observing Gotra during rituals and Marriages. The term Gotra broadly refers to people who are descendants in an unbroken male line from a common male ancestor.

Ayurveda or ayurvedic medicine is a system of traditional medicine native to India and a form of alternative medicine. In Sanskrit, words , meaning "longevity", and , meaning "knowledge" or "science". The earliest literature on Indian medical practice appeared during the Vedic period in India,...

 clearly states that marriage within the Gotra is a consanguineous marriage which can lead to many gestational and genetic problems in the fetus. So it has become a common practice in the Hindu households during pre-marriage discussions to ask the couples' Gotra. Couples of the same Gotra are advised not to marry. The advisers of this system say that this practice definitely helps in reducing the gestational problems and ensures a healthy progeny.

Rates of occurrence

Historically, some Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

an nobles cited a close degree of consanguinity when they required convenient grounds for divorce
Divorce is the final termination of a marital union, canceling the legal duties and responsibilities of marriage and dissolving the bonds of matrimony between the parties...

, especially in contexts where religious
Religion is a collection of cultural systems, belief systems, and worldviews that establishes symbols that relate humanity to spirituality and, sometimes, to moral values. Many religions have narratives, symbols, traditions and sacred histories that are intended to give meaning to life or to...

 doctrine forbade the voluntary dissolution of an unhappy or childless marriage. Conversely, the consanguinity law of succession
Order of succession
An order of succession is a formula or algorithm that determines who inherits an office upon the death, resignation, or removal of its current occupant.-Monarchies and nobility:...

 requires the next monarch
A monarch is the person who heads a monarchy. This is a form of government in which a state or polity is ruled or controlled by an individual who typically inherits the throne by birth and occasionally rules for life or until abdication...

 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 muslim 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
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...

. This means that they carry two copies (alleles) of the same gene. Except in certain rare circumstances (new mutations or uniparental disomy
Uniparental disomy
Uniparental disomy occurs when a person receives two copies of a chromosome, or part of a chromosome, from one parent and no copies from the other parent.. UPD could involve isodisomy or heterodisomy ....

) 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 the risk is greater in mating relationships where the parents are close relatives, but for relationships between more distant relatives, such as second cousins, the risk is lower (although still greater than the general population).

The low genetic heterozygosity associated with increased consanguinity in a population (identified by microsatellite markers) increases its susceptibility to infectious pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...

s such as tuberculosis
Tuberculosis, MTB, or TB is a common, and in many cases lethal, infectious disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis. Tuberculosis usually attacks the lungs but can also affect other parts of the body...

 and hepatitis
Hepatitis is a medical condition defined by the inflammation of the liver and characterized by the presence of inflammatory cells in the tissue of the organ. The name is from the Greek hepar , the root being hepat- , meaning liver, and suffix -itis, meaning "inflammation"...


See also

External links

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