How to Count Degrees of Kinship in Japan, with a Chart: Which Relatives Fall in the 1st to 6th Degree and Who Counts as a Relative

A degree of kinship is the number of generations between you and a relative

A degree of kinship (shintō) is a number showing how closely you're related to someone. Article 726 of Japan's Civil Code sets out how to count it: you count the parent–child generations between yourself and the other person. The smaller the number, the closer the relative. Parents and children are 1st degree, grandparents and grandchildren are 2nd degree.

Degrees are only counted for blood relatives and for in-laws created by marriage. A spouse (husband or wife) is a relative under the Civil Code but has no degree. It isn't counted as "0th degree" either, so forms and rules usually mention the spouse separately, as in "spouse and relatives within the Nth degree".

• Blood relatives: relatives by blood, such as parents, grandparents, children, grandchildren, siblings, uncles and aunts, and cousins. Adoptive parents and adopted children are also blood relatives (legal blood relatives).
• In-laws: relatives created by marriage. Your spouse's blood relatives (parents-in-law, your spouse's siblings, etc.) and the spouses of your blood relatives (a brother's wife, a son's wife, etc.).
• Spouse: your husband or wife. A relative, but with no degree.

How to count: lineal relatives by generations, collateral relatives by steps up plus steps down

How you count depends on whether the person is a lineal relative directly above or below you, or a collateral relative on a branch. In both cases the idea is the same: add 1 for each generation you pass through.

1. 1

   For lineal relatives, the number of generations is the degree

   For people you can trace straight up (parents, grandparents, great-grandparents) or straight down (children, grandchildren, great-grandchildren), the number of generations between you is the degree. Grandparents are 2 generations up, so 2nd degree; great-grandchildren are 3 generations down, so 3rd degree.

2. 2

   For collateral relatives, first go up to the common ancestor

   For siblings, uncles and aunts, cousins and so on, count how many generations you go up from yourself to the ancestor you share (a parent, grandparent, etc.).

3. 3

   Then add the steps down to the other person

   Count how many generations down it is from the common ancestor to the other person, and add it to the steps up. For a cousin, you go up 2 generations to your shared grandparents, then down 2 through the uncle or aunt to the cousin, so 2 + 2 = 4th degree.

Counted this way, siblings are "1 up to a parent, then 1 down", so 2nd degree. Siblings feel like your closest relatives, but they aren't 1st degree. Likewise, uncles and aunts (your parents' siblings) are 1 up to a parent and 2 down, so 3rd degree, and nephews and nieces are 1 up and 2 down, also 3rd degree.

Chart of the 1st to 6th degree

Here are commonly looked-up relationships arranged by degree. Blood relatives are on the left and in-laws on the right. For in-laws, put your spouse in your own position; the spouse of a blood relative has the same degree as that relative (details in What are in-laws? What degree is a brother- or sister-in-law?).

Beyond the 4th degree, many people don't know the names. Why a cousin's child and a parent's cousin share one name, and how second and third cousins differ, are explained in Second cousins and cousins once removed: the differences and what to call them. The Japanese characters for elder and younger uncles and aunts, great-uncles and grandnephews are covered in Elder vs. younger uncles in Japanese, and a list of family terms.

Under the Civil Code, "relatives" are blood relatives to the 6th degree, the spouse and in-laws to the 3rd degree

Article 725 of the Civil Code defines relatives as "blood relatives within the 6th degree", "the spouse" and "in-laws within the 3rd degree". In the chart, blood relatives up to second cousins (6th degree) and in-laws up to your spouse's uncles, aunts, nephews and nieces and the spouses of your uncles and aunts (3rd degree) are relatives under the Civil Code.

• A second cousin's child (7th degree) and third cousins (8th degree) are related by blood but are not relatives under the Civil Code.
• Your spouse's cousins (4th-degree in-laws) are not relatives.
• Men married to sisters, women married to brothers, and the parents of your brother's wife or your son's wife don't even have a degree; legally they are strangers.

When a company's condolence policy, an insurance policy or an application form says "relatives within the 3rd degree", it usually means blood relatives and in-laws up to the 3rd degree, plus the spouse. For blood relatives that's up to great-grandparents, great-grandchildren, uncles and aunts, and nephews and nieces; for in-laws, up to your spouse's uncles, aunts, nephews and nieces. Cousins are 4th degree, so they're not included. Some rules are limited to blood relatives, as in "blood relatives within the 2nd degree", so read carefully enough to see whether in-laws are included.

Marriage, support and inheritance rules set by degree

Degrees of kinship are used to draw the line in several Civil Code rules. Here are the main ones.

Inheritance isn't decided by degree alone but by order of priority. Grandparents, for example, are 2nd degree but don't inherit if there are children or grandchildren. Conversely, if a child has already died, that child's child (a grandchild) inherits in their place, even though they're 2nd degree. Note also that representation for nephews and nieces goes only one generation and doesn't pass to their children (grandnephews and grandnieces).

They aren't law, but bereavement leave and mourning postcards are also often scoped by degree. Days and guidelines by relationship are in Bereavement leave and mourning in Japan: how many degrees of kinship?.

5 points people often count wrong

• Siblings are 2nd degree: you pass through a parent, so 1 + 1 = 2. If you think "they're closest, so 1st degree", every number after that is off by one.
• A spouse has no degree: neither 0th nor 1st. When counting your spouse's blood relatives, put your spouse in your own position.
• Don't count yourself: you are the starting point at 0; count only the generations you pass through.
• Brothers- and sisters-in-law are 2nd-degree in-laws: both your spouse's siblings and your siblings' spouses are 2nd degree. They're not blood relatives, so they don't inherit.
• Half-siblings are blood relatives too: siblings who share only one parent are 2nd-degree blood relatives through that parent (their inheritance share is half that of full siblings).

Once a relationship gets long, counting in your head is hard. In the Kinship Degree & Relationship Calculator, just tap "Father", "Older brother", "Son" and so on in order starting from yourself, and it shows the degree, what the relative is called and whether they're a relative under the Civil Code, with a family tree and the "steps up + steps down" formula so you can see how it was counted. If you know the name of the relationship, you can also find it in the chart, such as "second cousin" or "brother-in-law", and tap it.

FAQ

What degree of kinship is a brother or sister?

2nd-degree collateral blood relative. You go up 1 generation to your parent, the common ancestor, and then down 1, so 1 + 1 = 2nd degree. Only parents and children are 1st degree.

What degree of kinship is a spouse?

A spouse has no degree. They're a relative under the Civil Code, but degrees are only used for blood relatives and in-laws, and a spouse isn't counted as 0th degree either. That's why rules and forms mention the spouse separately, as in "spouse and relatives within the 3rd degree".

Who is in the 3rd degree?

Among blood relatives: great-grandparents, great-grandchildren, uncles and aunts, and nephews and nieces. Among in-laws: your spouse's uncles, aunts, nephews and nieces, spouses of your uncles and aunts, spouses of your nephews and nieces, and your spouse's great-grandparents. Cousins are 4th degree, so they're not included.

Is a cousin a legal relative?

Yes. A cousin is a 4th-degree collateral blood relative (2 generations up to your grandparents and 2 down), which falls within the Civil Code's relatives (blood relatives within the 6th degree). Relatives go as far as second cousins (6th degree); a second cousin's child (7th degree) is not a relative.

Is there an easy way to look up the degree?

With the Kinship Degree & Relationship Calculator, tap Father, Mother, Older brother, Older sister, Younger brother, Younger sister, Son, Daughter, Husband or Wife in order from yourself, and it shows the degree, the name of the relationship, whether it's a blood or in-law relationship, and whether the person is a relative under the Civil Code. It also shows a family tree and the counting formula.