Consanguinity facts for kids
Consanguinity means being related by blood to another person. It's like saying you share the same family tree or have a common ancestor. Rules about consanguinity help decide who inherits things when someone passes away without a will. These rules can be different depending on where you live.
Contents
History of Blood Relations
Most cultures throughout history have said that people who are closely related by blood should not marry. However, there were some exceptions. For example, in ancient Egypt, brothers and sisters sometimes married, especially within the royal family. Some people believe this helped a King keep his power. In the Bible, Abraham married his half-sister, Sarah.
Roman Laws on Marriage
In ancient Rome, marriage rules came from civil laws. These laws said that people could not marry if they were within four "degrees" of blood relation. The Germanic peoples also had rules against such marriages, but they were not as strict.
Marriage Rules in Medieval Europe
After the Roman Empire ended in the 5th century, the Church slowly started to make rules about marriage. At first, the Church followed the Roman civil laws.
Later, in the 9th century, the Church made the rules much stricter. They increased the number of forbidden "degrees" of relation to seven. They also changed how these degrees were counted. This became a problem for the nobility in Europe. Noble families often married within their own social class. Eventually, many noble families became too closely related to marry under the Church's new rules. This meant many had to go against the Church's laws.
In 1215, a big meeting called the Fourth Council of the Lateran changed the rules again. They reduced the number of forbidden degrees of blood relation back to four. The pope (the leader of the Catholic Church) could give special permission, called a papal dispensation, for closely related couples to marry. This special permission was almost always given only to royalty and noble families.
Sometimes, the Church used these rules to stop a marriage. For example, William the Conqueror and Matilda of Flanders were cousins. In 1049, Pope Leo IX said they could not marry. But they got married anyway! Ten years later, in 1059, Pope, Nicholas II finally gave them special permission for their marriage. Even with these rules and laws, marriages between blood relatives were still common in Europe until the 20th century.
Understanding Common Ancestors
You can see how closely people are related using a consanguinity table. This table shows different generations as rows. People who are related through a shared ancestor, but not directly (like a parent and child), are called "collateral" relatives. This means they are like cousins, aunts, or uncles.
Consanguinity (being related by blood) is different from Affinity (being related through marriage, like in-laws). However, in the past, both types of relationships had similar rules about who could marry.
How Genetics Shows Relatedness
The table below shows how much DNA people who are related usually share. This is a way to understand how close your blood relationship is.
| Average DNA shared % |
Relationship |
|---|---|
| 100% | identical twin |
| 50% | parent / child |
| 25% | grandparent / grandchild |
| 12.5% | great-grandparent / great-grandchild |
| 6.25% | great-great-grandparent / great-great-grandchild |
| 3.125% | great-great-great-grandparent / great-great-great-grandchild |
| 50% | full sibling (brother/sister) |
| 37.5% | three-quarter-sibling |
| 25% | half-sibling |
| 12.5% | First cousin |
| 6.25% | First cousin once removed |
| 3.13% | Second cousin |
Related pages
Images for kids
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Consanguinity of the kings of France as shown in Arbor genealogiae regum Francorum (Bernard Gui, early 14th century).
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A simple picture showing how genes are passed down through generations.
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This diagram shows common family relationships. The size of each colored circle shows how closely related people are.
See also
In Spanish: Consanguinidad para niños
