Can you marry a sibling in Japan?

Can siblings marry in Japan? The straight answer is no. Marriage between blood-related siblings, or bigamy, is prohibited in Japan, as it is in most countries throughout the world.

But sometimes there is no choosing who you fall in love with, so let’s look at marriage between relatives in Japan.

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The Law on Siblings Marrying in Japan

Can you marry a sibling in Japan? 1

According to Japanese law, lineal relatives by blood (within the third degree of kinship) may not marry. However, this law does not include marriage between adopted children and their relatives by blood through adoption. 

You can marry an adopted sibling. However, adoption is not a common practice in Japan.

Although marriage between siblings is not lawful in Japan today, that does not mean that it wasn’t an unknown practice throughout the world in times gone past. 

Ruling Inca kings were expected to marry their full sisters, and Pharaohs in Egypt married their sisters to retain their religious and culturally important roles.

It’s not an accepted practice today, mainly because the children of these unions were prone to genetic disorders. But in times gone past, it was an integral aspect of the highest leadership in royal families. 

Other Forms of Family Law in Japan

While marrying your sibling is not legal, you can marry your cousin in Japan. Consanguinity, or marriage between cousins, has been a common trend throughout the world in years gone past. 

Many famous people have married their cousins, including Japan’s Prime Minister, Naoto Kan, Albert Einstein, Queen Elizabeth and Prince Phillip of Britain, and Kevin Bacon.

Reasons Why Consanguinity was Prevalent in Japan

Consanguinity was a common practice that occurred in arranged marriages. These arranged marriages between cousins retained the family’s wealth, prevented cultural values from disappearing, and kept the family ties strong. 

Due to several geographic reasons, the same reason the sun rises early, Japanese families would encourage consanguinity amongst their younger generations. Japan is fairly isolated from its neighbors, with steep mountains that create small communities. 

These sometimes inbred communities developed their own particular cultures, like using socks with sandals and emphasizing pride in heritage and traditions.

The stratified class system in Japan before the Meiji Restoration also prevented intermarriage between social classes, limiting available marriage options.

Marriage Between Cousins Today in Japan

In Japan, marriage between cousins is legal but has lost most of its appeal.

The practice began dying out sometime after 1967 due to nuclear families shrinking inside and modern transportation that made travel so easy to previously isolated areas.

Industrialization also played a role in encouraging unmarried young people to flock to city centers where there were other options for marriage besides consanguinity.

Birth Defects in Offspring from Consanguinity 

The most crucial factor that has made marriage between cousins an uncommon practice in Japan is education.

Education has taught modern generations that marriage between cousins causes serious genetic disorders in the offspring of the union. Genetic disorders are less prevalent in offspring between siblings than between cousins. 

A cleft lip and palate, polydactyly, spina bifida, psychiatric conditions, and many other life-threatening diseases are present in offspring between cousins. 

Can you marry your cousin in Japan? Yes, you can. But it’s not a common practice to embrace in today’s modern times with the awareness of genetic disorders.

To learn more about Japan and its culture, read our article on why the Japanese don’t shave.