What Are In-Laws Under Japanese Law? The Degree of Parents-, Brothers- and Sisters-in-Law, and Whether Co-Brothers-in-Law and Co-Parents-in-Law Count as Relatives
Marriage suddenly brings a lot of relatives you're not related to by blood: your spouse's parents and siblings, your siblings' spouses, and so on. Japanese law calls them in-laws (inzoku) and counts their degree of kinship the same way as for blood relatives. This article explains the scope of in-laws and how to count their degree, gives a chart of the degree of parents-in-law, brothers- and sisters-in-law, daughters- and sons-in-law, explains why men married to sisters, women married to brothers and the two sets of parents of a married couple are not legally relatives, how in-laws are treated in inheritance and support, and the notice that ends the in-law relationship after divorce or a spouse's death.
In-laws are your spouse's blood relatives and your blood relatives' spouses
In-laws (inzoku) are relatives created by marriage. Under Japan's Civil Code, two kinds of people are in-laws.
- Your spouse's blood relatives: your spouse's parents (parents-in-law), your spouse's siblings (brothers- and sisters-in-law), your spouse's grandparents, your spouse's children from a previous relationship, etc.
- The spouses of your own blood relatives: your siblings' spouses (a brother's wife, a sister's husband, etc.), your children's spouses (daughters- and sons-in-law), your grandchildren's spouses, the spouses of your uncles and aunts, etc.
Your spouse is not an in-law but a separate kind of relative, "the spouse". Blood relatives on each side, such as your parents and your spouse's parents, are not in-laws of each other either. In-laws are always counted from you, with exactly one spouse in between.
How to count an in-law's degree
The degree of an in-law is counted exactly as for blood relatives. The key is where you place the spouse.
- 1
For your spouse's blood relatives, put your spouse in your position
Start from your spouse and count as you would for blood relatives. Your wife's father is 1 generation above your wife, so 1st degree. Your husband's older brother is 2nd degree from your husband, so he's a 2nd-degree in-law from you as well.
- 2
A blood relative's spouse has the same degree as that relative
Your brother's wife is the spouse of your brother (a 2nd-degree blood relative), so she's 2nd degree. Your son's wife is the spouse of your son (1st degree), so she's a 1st-degree in-law. Spouses have no degree, so nothing is added.
So the two people you'd call "brother-in-law", your spouse's brother (your spouse's blood relative) and your sister's husband (your blood relative's spouse), are traced differently but are both 2nd-degree collateral in-laws. How to count blood relatives is explained in How to count degrees of kinship, with a chart.
In-law chart: 1st to 3rd degree
| Degree | Spouse's blood relatives | Blood relatives' spouses |
|---|---|---|
| 1st | Father- and mother-in-law; spouse's child from a previous relationship (stepchild) | Daughter- or son-in-law (child's spouse); stepfather or stepmother (parent's new spouse) |
| 2nd | Spouse's grandparents; spouse's siblings (brothers- and sisters-in-law) | Brother's wife, sister's husband, grandchild's spouse, grandparent's new spouse |
| 3rd | Spouse's great-grandparents, spouse's uncles and aunts, spouse's nephews and nieces | Spouses of uncles and aunts (uncle or aunt by marriage), spouses of nephews and nieces, spouses of great-grandchildren |
In-laws count as relatives under the Civil Code only up to the 3rd degree. Your spouse's cousins (4th degree) and your cousins' spouses (4th degree) are not legal relatives, however close the family ties.
Japanese terms for in-laws and how to read them
Japanese has traditional terms for in-laws and modern ones formed with 義 (gi, "in-law"). Both refer to the same people, but some readings are easy to get wrong, so here they are side by side.
| Relationship | Japanese terms | Reading | Degree |
|---|---|---|---|
| Spouse's father | 舅, 義父 | shūto, gifu | 1st |
| Spouse's mother | 姑, 義母 | shūtome, gibo | 1st |
| Spouse's brother | 小舅, 義兄, 義弟 | kojūto, gikei, gitei | 2nd |
| Spouse's sister | 小姑, 義姉, 義妹 | kojūtome, gishi, gimai | 2nd |
| Older or younger brother's wife | 兄嫁, 弟嫁 (義姉, 義妹) | aniyome, otōtoyome | 2nd |
| Older or younger sister's husband | 義兄, 義弟 | gikei, gitei | 2nd |
| Son's wife, daughter's husband | 嫁, 婿 | yome, muko | 1st |
| Father's new wife, mother's new husband | 継母, 継父 | keibo (mamahaha), keifu (mamachichi) | 1st |
義兄 (gikei) is used both for your spouse's older brother and your older sister's husband, so the written word alone doesn't tell you which. Where accuracy matters, such as bereavement leave requests or inheritance documents, write the relationship out ("my wife's older brother", "my older sister's husband") to avoid confusion. When addressing them, the characters are written with 義 but read as the ordinary words for older brother and mother (oniisan, okaasan).
Co-brothers-in-law, co-sisters-in-law and co-parents-in-law are legally strangers
Some relationships feel close in family life but are not relatives under the Civil Code. The three typical ones are below.
| Japanese term | Reading | Relationship | Relative? |
|---|---|---|---|
| 相婿 | aimuko | Men whose wives are sisters (your wife's sister's husband) | No |
| 相嫁 | aiyome | Women whose husbands are brothers (your husband's brother's wife) | No |
| 相舅 | aiyake | Parents whose children are married to each other (your child's spouse's parents) | No |
Co-brothers-in-law and co-sisters-in-law are "the spouse of a blood relative of your spouse", and co-parents-in-law are "the blood relatives of a blood relative's spouse". In-laws only go as far as relationships with one spouse in between, so relationships with two spouses in between, or the blood relatives of in-laws, fall outside the scope of relatives. Your brother's wife's parents and your sister's husband's siblings are likewise legally strangers.
Even so, people still call co-brothers-in-law "brothers by marriage", and at weddings the two sets of parents may greet each other as aiyake. Think of legal relative status and family ties as separate things.
How in-laws are treated in inheritance, support and marriage
- Inheritance: in-laws are not statutory heirs. A daughter-in-law who cared for her parents-in-law for years cannot inherit without a will or adoption. However, a relative who provided unpaid care or nursing and made a special contribution to preserving the estate can claim a "special contribution payment" from the heirs (Civil Code Art. 1050).
- Support: in-laws normally have no duty of support. For in-laws within the 3rd degree, a family court may impose a duty of support only in special circumstances (Civil Code Art. 877, para. 2).
- Marriage: you cannot marry a lineal in-law (parents-in-law, a child's spouse, etc.), even after the in-law relationship ends through divorce or death (Civil Code Art. 735). You can marry a collateral in-law, such as your spouse's sibling, after divorce from or the death of your spouse.
- Bereavement leave: some companies cover parents-in-law and a spouse's grandparents and siblings. Examples of leave days are in Bereavement leave and mourning in Japan: how many degrees of kinship?.
In-law relationships after divorce or death, and the notice ending them
In-law relationships end automatically on divorce. When a spouse dies, however, the in-law relationship continues as it is. If the surviving spouse wants to end it, they submit a "notice of termination of in-law relationship" (inzoku kankei shūryō todoke) to the city, ward, town or village office (Civil Code Art. 728).
- Only the surviving spouse can file it; the consent of the parents-in-law or anyone else on the other side is not needed.
- There's no deadline; it can be filed any number of years after the spouse's death.
- Filing it doesn't require returning anything already inherited from the deceased spouse.
- The relationship between your children and the deceased spouse's parents (the children's grandparents) doesn't change. To the children they remain blood relatives.
- Your surname and family register stay as they are. To return to your former surname, you file a separate notice (fukuushi todoke).
When a relationship gets complicated and you can't tell whether someone is an in-law, or a relative at all, try tapping it out from yourself in the Kinship Degree & Relationship Calculator, such as "Wife → Older sister → Husband" (co-brother-in-law) or "Son → Wife → Father" (co-parent-in-law). It shows together whether they're an in-law, whether they're a relative under the Civil Code and whether they'd be an heir.
FAQ
- What degree of kinship is my spouse's brother or sister?
- 2nd-degree collateral in-law. If you put your spouse in your own position, your spouse's siblings are 2nd degree from your spouse, so they're 2nd degree from you too. They're relatives under the Civil Code but not statutory heirs.
- What degree is my brother's wife or my sister's husband?
- Both are 2nd-degree collateral in-laws. A blood relative's spouse is counted at the same degree as that relative. Your brother or sister is a 2nd-degree blood relative, so their spouse is 2nd degree too.
- What degree are my parents-in-law?
- 1st-degree lineal in-laws. You cannot marry a lineal in-law even after the in-law relationship ends through divorce or death (Civil Code Art. 735). They're not heirs, but as in-laws within the 3rd degree, a family court may impose a duty of support in special circumstances.
- Is a co-brother-in-law (aimuko) a relative?
- Not under the Civil Code. Co-brothers-in-law are men married to sisters; each is the spouse of a blood relative of the other's spouse. In-laws only go as far as relationships with one spouse in between, so co-brothers-in-law, co-sisters-in-law and co-parents-in-law are legally strangers.
- What happens to my relationship with my parents-in-law if my spouse dies?
- The in-law relationship continues as it is. To end it, submit a notice of termination of in-law relationship to your municipal office. Your parents-in-law's consent isn't needed and there's no deadline. The relationship between your children and their grandparents doesn't change.
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