Consanguinity is the sharing of a blood relationship with another person. An example of consanguinity is the relationship that exists between a brother and sister. When it comes to the law, the term consanguinity is often used when defining the boundaries of marriage and sexual relations, which are of course prohibited between blood relatives. To explore this concept, consider the following consanguinity definition.

Definition of Consanguinity


  1. A relationship by descent; having a common ancestor.
  2. The blood relationship that exists between two people.


1350-1400       Latin    consanguinitās

What is Consanguinity

Consanguinity is the state of being related to someone else as the result of sharing an ancestor. The term “consanguinity” is often used in relation with marriages or sexual relations between relatives, and whether they are prohibited by law. Examples of consanguinity can be measured in degrees of how closely related two people are to each other, such as parent and child (first degree), or half-siblings (second degree). The highest degree is fifth degree, which is what second cousins are considered. This means that this is the loosest biological relation that can possibly exist.

Put another way, parents and children share one out of every two genes, which makes them related in the first degree. However, second cousins only share one gene out of every 32 genes, which makes them only loosely related to each other.

Consanguinity is also considered when a court is determining someone’s inheritance. Generally, the closer the person is to the deceased, the more of an inheritance he will be awarded by the court. This is why children tend to inherit their parents’ entire estate without any questions being asked, insofar as the law is concerned.

If someone who does not have children dies, however, his estate is awarded to his spouse or to his closest living relative, which may be a parent. If the person’s parents are also dead, however, then the legality can become messy when trying to determine which relatives are entitled to an inheritance, and how much of an inheritance they are entitled to.

Consanguinity and Incest

Incest is defined differently, depending on whether it is being defined legally or biologically. Biologically speaking, incest refers to intimate relationships between first-degree blood relatives. An example of consanguinity and biological incest includes an intimate relationship between parents and offspring, siblings, or even between aunts and uncles and their nieces and nephews. Legally speaking, however, incest can also include relationships between relatives who are related by marriage, and not by blood; such as between stepparents and their spouses’ children, or between step-siblings.

Incest is illegal in most parts of North America. In the U.S., the legality of marriages between people who are blood related varies by state, though it is legal, in about have of the states, to marry a first cousin – which is a third-degree relationship.

Globally, there are plenty of cultures that not only accept incestuous relationships, but which encourage and celebrate them. Incest relationships are particularly common in places like Asia, Africa, and the Middle East. In fact, there are some areas of the world where between 20 and 60 percent of married persons, are married to a close biological relative.

Consanguineous Marriage

Depending on the culture, consanguineous marriage may either be illegal and stigmatized, or encouraged and celebrated. Different parts of the world have very different rules when it comes to whether or not to outlaw consanguineous marriage. For the most part, consanguineous marriages are illegal throughout the United States. However, in other areas of the world, they are actually among the most common.

The reasons why consanguineous marriages are encouraged in some parts of the world and not others are strictly social. Cultures that encourage the practice believe that a higher level of compatibility exists between husbands and wives who are related to each other. They also believe that a higher compatibility exists between the couple and other members of their immediate family.

Consanguineous marriages are considered a status symbol in some countries, with the female benefiting in particular. One of the perceived benefits provided to the woman is a better relationship with her in-laws, which provides her with more support in harder times. Some cultures also believe that marriages between relatives will actually reduce the potential for issues related to health and finances. Cousin marriage in particular is celebrated for the belief that it upholds cultural values by strengthening the family, and encouraging solidarity. Landlords may also encourage consanguineous marriages for the purpose of keeping a piece of property within the family.

In those areas of the world where consanguineous marriages are accepted, couples may still be concerned about the genetic risks they are facing if they decide to have children together. It is for this reason that consanguineous couples are encouraged to seek both preconception and premarital counseling, so that they can make a more informed decision as to whether or not they should have children.


Consanguineous marriages were rather common throughout history among the noble class in Europe. Some nobles would deliberately marry relatives so that they could use their biological relation as an excuse to get divorced when either the relationship, soured or the wife was unable to get pregnant. Similarly, monarchs were required to be close blood relatives, to the point of sharing the same blood as the monarch who previously held the throne.

Middle East

It is common practice, even today, for Arabs to marry their close relatives. It is estimated that between 40 and 50 percent of all Arabian marriages are consanguineous. For instance, in Saudi Arabia, approximately 70 percent of all marriages are between close biological relatives. A similar situation exists in Kuwait, where nearly 55 percent of marriages are consanguineous as well.

Egypt’s culture, on the other hand, permits marriage between cousins, which accounts for about 40 percent of their marriages. Most of these marriages are between first cousins, which is a third-degree relationship. The same thing goes for Pakistan, where about 55 percent of marriages are between first cousins as well. It is preferred in Pakistani culture that the relationship specifically consist of a boy marrying the daughter of his father’s brother.

Consanguinity and Genetic Disorders

Incest is discouraged in many countries for a number of reasons, the most accepted of which being the fact that the closer the biological relationship, the higher the chances for genetic disorders in offspring, such as severe birth defects, or even the death of the child. For instance, while first-degree relatives who are in a relationship have about a 30 percent risk of bearing a child with either severe birth defects, or which is stillborn. The risk drops to about 2 to 3 percent for third-degree relatives (first cousins).

The risk of severe birth defects varies, depending on both the kind of society in which the relationship exists, and the way studies measure a child’s health during the first few years of its life. The reason why closer biological relationships are more likely to bear children with genetic disorders is because children of these unions are more likely to inherit exact copies of one or more damaged recessive genes.

For instance, if a child of a couple that is not biologically related, one of whom has a gene that puts him at risk for cystic fibrosis, that gene has a greater chance of multiplying significantly in a child born of an incestuous union. That child is therefore more likely to develop a genetic disorder. Interestingly, damaged chromosomes do not occur more often in incestuous relationships, so the odds of an incestuous relationship bearing a child with Down Syndrome are the same as those for the parents who are unrelated to each other.

Consanguinity Example in Adoption

In 1994, the Supreme Court of South Dakota heard the case of David Bale, a man who was proven to have engaged in sexual relations with his 19-year-old adopted daughter over the course of two months. The question the Court had to decide was whether or not sexual relations between an adoptive father and his adoptive daughter could still be legally considered incest, since the two were not biologically related.

The trial court found – and the Supreme Court agreed – that the relationship between Bale and his adopted daughter was not, in fact, an incestuous one. The State’s argument was that, because adoption creates a legal relationship between a parent and child, that parent then assumes all of the same duties and responsibilities for the child as a biological parent.

The Court, however, found that adoption does not automatically change the consanguinity of the relationship. The child is still biologically related to the parents that created him. The adoptive parent is not related to that child by blood and, as such, the Court ruled that a case for incest simply cannot be made in the state of South Dakota. This is because incest, as defined by South Dakota law, is limited only to those who are related by consanguinity.

Related Legal Terms and Issues

  • Incest – The crime of engaging in sexual relations with someone who is too closely related to that person to marry, such as a parent and his or her offspring.