Degrees of kinship are a numerical measure of how closely two people are related, counted by the generational steps between them. Courts use that number to decide who inherits when someone dies without a will, whether two relatives may legally marry, how an inheritance tax applies, and when a judge or official must step aside from a case involving family. A smaller number means a closer relationship and, in most legal situations, a stronger claim.
Two different counting systems exist, and they produce different numbers for the same relationship. A first cousin is a fourth-degree relative under one method and a second-degree relative under the other, so the first thing to know is which system your jurisdiction uses.
The Two Ways Degrees Are Counted
Civil Law Method
Nearly every U.S. state, along with the Uniform Probate Code, uses the civil law method (sometimes called the Roman law method). You start with yourself, count each generational step up to the nearest ancestor you share with the other person, then count each step back down to them. Add the two counts together. You exclude yourself from the count but include the other person.
- Parent or child: one step = first degree.
- Sibling: one step up to a shared parent, one step down = second degree.
- Grandparent or grandchild: two steps in a straight line = second degree.
- Aunt or uncle: two steps up to a shared grandparent, one step down = third degree.
- First cousin: two up, two down = fourth degree.
Canon Law Method
The canon law method counts collateral relatives differently. Instead of adding both sides of the path, you count the steps on each side separately and take the larger number. Siblings become first-degree relatives, first cousins become second-degree, and an uncle is second-degree rather than third. You will rarely see this method in an American courtroom, but it still appears in Catholic marriage dispensation rules and in older legal texts. If a document references kinship numbers that seem lower than you would expect, canon counting is the likely explanation.
Blood, Marriage, Direct, and Collateral
Before applying either count, you need to know which kind of relationship you are measuring. Legal kinship splits two ways.
Consanguinity covers people who share a biological ancestor: parents, siblings, grandparents, cousins, and so on. This is the category that drives most inheritance rules. Affinity covers connections created by marriage, the people you would call in-laws. Courts generally treat affinity as weaker than consanguinity. In most states, in-laws have no right to inherit from you under intestacy rules, and affinity typically dissolves at divorce. When a marriage ends by death rather than divorce, some states continue the affinity tie for certain purposes such as marriage-prohibition rules.
Within consanguinity, relationships split again. Lineal (or direct) relatives descend from one another in a straight vertical chain: you, your parents, grandparents going up, and your children and grandchildren going down. Collateral relatives share a common ancestor but do not descend from each other. Siblings, aunts, uncles, nieces, nephews, and cousins all branch off the lineal trunk, which is why calculating their degree requires counting up to the shared ancestor and back down the other branch.
Who Inherits When There Is No Will
Degrees of kinship do their heaviest work in intestate succession, the rules that take over when someone dies without a valid will. Closer relatives inherit before more distant ones, and within the same degree the law follows a set priority order. The details vary by state, but the Uniform Probate Code, adopted in whole or in part by roughly 18 states, provides a widely followed framework.
The typical order runs:
- Surviving spouse, who receives the entire estate or a large share depending on whether the deceased also left surviving descendants or parents.
- Descendants (children, then grandchildren). If no spouse survives, descendants take the entire estate. If a spouse survives alongside descendants, most states split the estate between them.
- Parents, if no descendants survive.
- Siblings and their descendants.
- Grandparents and their descendants, which is where aunts, uncles, and first cousins enter.
Courts work through this list from top to bottom and stop as soon as they find a living relative in a category. A surviving child blocks a sibling from inheriting anything at all.
If the court reaches the end of the list and finds no living relative within the recognized degrees, the estate passes to the state. The traditional term is escheat, though the Uniform Probate Code simply says the property passes to the state. Most statutes cast a wide enough net that a relative usually turns up, but for people with small or estranged families it is a real possibility. A will is the simplest way to prevent it, since a will lets you direct assets to friends, charities, or anyone else regardless of kinship.
How Shares Are Divided When an Heir Has Died First
Identifying who inherits is only half the problem. The other half is deciding what share each heir receives, especially when a person who would have inherited has already died. Two distribution methods dominate.
Per Stirpes
Per stirpes (Latin for “by branch”) divides the estate along family branches. Each branch stemming from the deceased gets an equal share, and if the head of a branch has already died, that branch’s share passes down to their descendants. Consider a parent with three children: Alan, Beth, and Claude. Alan dies first, leaving two children of his own. Under per stirpes, the estate splits into thirds. Beth and Claude each take one-third, and Alan’s two children split his one-third, receiving one-sixth each.
Per Capita at Each Generation
The Uniform Probate Code and a growing number of states use per capita at each generation, which pools and redistributes shares more evenly. The estate first divides into equal shares at the nearest generation with at least one surviving member. Living members of that generation each take one share. Any leftover shares that would have gone to deceased members are combined and redistributed equally among the next generation of surviving descendants.
In the same family, Beth and Claude each take one-third. Alan’s one-third drops into a pool rather than flowing straight to his two children. If Beth and Claude also had predeceased children with living descendants, all of those next-generation descendants split the pooled remainder equally. The practical effect is that members of the same generation always receive equal shares, regardless of which branch they belong to.
How Modern Law Treats Adopted, Half-Blood, and Non-Marital Children
In the vast majority of states, an adopted child is treated as the legal child of the adoptive parents for all inheritance purposes, with the same rights as a biological child. Adoption typically severs the legal parent-child relationship with the biological parents, which means the adopted child no longer inherits from them through intestacy. Stepparent adoptions are the major exception: when a stepparent adopts a spouse’s child, the child’s relationship with that biological parent remains intact, and the child can inherit from both sides.
Half-siblings inherit on equal footing with full siblings under the Uniform Probate Code and in most states. A half-brother has the same legal claim to your intestate estate as a full brother. A small number of states give half-blood relatives a reduced share.
Children born outside of marriage can inherit from both biological parents, but they sometimes face the practical burden of proving parentage. If paternity was legally established during the parent’s lifetime through a court order, voluntary acknowledgment, or the parent openly treating the child as their own, inheritance rights follow automatically. When parentage was never formally established, the child may need to prove the biological relationship in probate, often by clear and convincing evidence.
When a Close Relative Still Does Not Inherit
Being next in line on the kinship chart does not always guarantee you will inherit. The most dramatic bar is the slayer rule, which prevents a person who intentionally and unlawfully kills the decedent from benefiting from the death. Courts treat the killer as though they died before the victim, which removes them from the succession line and lets the estate pass to the next eligible heir. A murder conviction creates an automatic presumption that the rule applies, but a conviction is not required: probate courts can apply the rule based on civil evidence even if the criminal case ended in acquittal or was never brought.
Other grounds for disqualification vary by state but commonly include abandonment of a minor child by a parent, which can bar the parent from inheriting from the child, and certain types of elder abuse or financial exploitation. A person can also voluntarily disclaim an inheritance by formally refusing it, which causes the estate to pass as though that heir had predeceased the decedent.
Other Places Kinship Degrees Show Up
Succession is the most common context, but the same framework appears elsewhere in the law.
Every state prohibits marriage between lineal relatives and between siblings, including half-siblings. Rules diverge for more distant relatives: roughly half of states allow first-cousin marriages, while the rest prohibit them or allow them only under specific conditions such as age thresholds or genetic counseling requirements.
Inheritance taxes, which a handful of states still impose, use kinship classes to set rates. The closer the relationship, the lower the tax and the higher the exemption. Surviving spouses are typically exempt entirely, and lineal descendants often pay little or nothing. Distant relatives and unrelated beneficiaries face the steepest rates, which can reach 16% in some states. As of 2026, only five states maintain a standalone inheritance tax, and one additional state imposes both an estate tax and an inheritance tax.
Conflict-of-interest and recusal rules reference kinship degrees as well. A judge related to a party within a specified degree must typically step aside, and public officials may be barred from voting on matters that financially benefit close relatives. Immigration law uses kinship categories to set visa preference levels, with immediate relatives of U.S. citizens receiving priority over more distant family connections.