A table of consanguinity is a chart that maps blood relationships around one person and assigns each relative a numbered “degree” of kinship. That degree is not just genealogy trivia. It decides who inherits when someone dies without a will, who is allowed to marry, who a federal official is barred from hiring, and who gets to make medical decisions for a relative who can’t speak for themselves.
How to Read the Chart
A standard table is a grid with one person labeled “Self” at the center. The vertical column running straight above and below Self holds the lineal relatives: parents, grandparents, and great-grandparents above; children, grandchildren, and great-grandchildren below. Every other cell branches sideways from that column to show collateral relatives: siblings, aunts and uncles, cousins, nieces and nephews, and their descendants.
To find your relationship to another person on the chart, locate the nearest ancestor the two of you share. Trace one path down from that ancestor to yourself and another path down to the other person. The cell where those two paths meet gives you the relationship name and the degree number. A lower number means a closer blood connection; a higher number means a more distant one.
Lineal and Collateral Relatives
Lineal consanguinity is the straight vertical line of descent: parent to child, grandparent to grandchild, great-grandparent to great-grandchild. Each generation in that direct chain adds one degree. Your parent is one degree away, your grandparent two, your great-grandparent three.
Collateral consanguinity covers everyone who shares an ancestor with you but doesn’t sit directly above or below you. Siblings, aunts, uncles, cousins, nieces, and nephews all branch sideways on the chart. Collateral relatives are always more degrees apart than lineal relatives at the same generational level, because the count has to travel up to the shared ancestor and then back down the other branch.
How Degrees Are Counted
American courts and most secular legal systems use the civil law method. You count every generational step between the two relatives, going up to the nearest common ancestor and then back down the other side, skipping the starting person. The distance from you to a first cousin works out to four degrees: two steps up to the shared grandparent, then two steps back down to the cousin.1U.S. Department of State Foreign Affairs Manual. 7 FAM 200 Appendix D – Identifying Next of Kin or Legal Representative Siblings are two degrees apart. An aunt or uncle is three.
The Catholic Church uses its own system under the 1983 Code of Canon Law. It counts all the persons in both lines combined, excluding the common ancestor, which in practice produces the same number as the civil method.2Vatican. Code of Canon Law – Physical and Juridic Persons Cann 96-123 First cousins are fourth-degree relatives under both systems today. Before 1983 the Church used an older Germanic approach that looked only at the longer branch from the common ancestor, which counted first cousins as second degree. Older genealogy sources that still use that method will show different numbers for the same relationship.
Cousin Labels and “Removed”
Cousin terminology trips up almost everyone, but the pattern is consistent. First cousins share a set of grandparents. Second cousins share a set of great-grandparents. Third cousins share great-great-grandparents.3Britannica. Cousin The cousin number matches the number of “greats” in the title of the nearest common ancestor, plus one.
“Removed” describes a generational gap between two cousins. Your first cousin’s child is your first cousin once removed: you share grandparents with the parent, but the child sits one generation below that. Your first cousin’s grandchild is your first cousin twice removed. The cousin number stays anchored to the closer generation, and the “removed” count tells you how many rows apart the two people sit on the grid.
Who Inherits Without a Will
When a person dies without a valid will, state probate law decides who inherits, and the degree of consanguinity drives the priority list. Under the Uniform Probate Code, adopted in whole or in part by 18 states, the estate passes first to the surviving spouse, then flows through relatives in order: the deceased’s children and their descendants, then parents, then siblings and their descendants, then grandparents and their descendants.1U.S. Department of State Foreign Affairs Manual. 7 FAM 200 Appendix D – Identifying Next of Kin or Legal Representative Each tier inherits only if no one in a closer tier survives.
States that haven’t adopted the UPC generally follow a similar descending pattern, though the specifics vary. Some cut off inheritance rights at a certain degree of kinship; others allow very distant relatives to inherit if no closer ones exist. Five states also impose a separate inheritance tax where the rate depends on how closely the heir was related to the deceased, with closer relatives paying lower rates or qualifying for larger exemptions.
Who Can Marry Whom
Every U.S. state prohibits marriage between lineal relatives (parents and children, grandparents and grandchildren) and between siblings, including half-siblings. Beyond that core, roughly half the states also ban first-cousin marriages. A smaller number allow first-cousin marriages only with conditions, such as both parties being above a certain age or one being unable to reproduce.
Canon law is stricter. Under Canon 1091, marriage is invalid between all lineal relatives and between collateral relatives up to and including the fourth degree, meaning first cousins cannot marry in the Catholic Church without a special dispensation.4Vatican. Code of Canon Law – Book IV – Function of the Church Liber A marriage performed in violation is void, not merely voidable.
In civil law, marrying within prohibited degrees can lead to annulment and, depending on the jurisdiction, criminal charges. Most states classify sexual relations between close relatives as a felony whether or not any marriage ceremony took place.
Federal Anti-Nepotism Rules
Federal law uses a consanguinity-based list to stop government officials from hiring their own relatives. Under 5 U.S.C. ยง 3110, a public official cannot appoint, promote, or advocate for hiring any “relative” into a civilian position in the official’s agency. The statute defines “relative” to include parents, children, siblings, aunts, uncles, first cousins, nieces, nephews, in-laws, step-relatives, and half-siblings.5Office of the Law Revision Counsel. 5 USC 3110 – Employment of Relatives Restrictions That reaches relatives up to the third degree on the civil law scale, plus the corresponding in-law and step-relationships.
The penalty is financial rather than criminal. A person hired in violation of the statute is not entitled to pay, and the Treasury cannot disburse funds to compensate them.5Office of the Law Revision Counsel. 5 USC 3110 – Employment of Relatives Restrictions Many state and local governments have parallel nepotism statutes with their own kinship lists, some narrower and some broader than the federal rule.
Who Decides Medical Care
When a person becomes incapacitated and has no healthcare power of attorney on file, most states assign decision-making authority to family members in a hierarchy that mirrors the consanguinity chart. The typical statutory priority runs from spouse to adult children, then parents, then adult siblings. Some states extend the list further to include grandchildren, nieces, nephews, and other relatives, with close friends sometimes appearing at the bottom.
If two family members at the same priority level disagree about treatment, the hospital or care facility may require a court to resolve the conflict. A healthcare directive or power of attorney sidesteps the hierarchy entirely, which is why estate planners push these documents even for young, healthy adults.
Social Security Survivor Benefits
Social Security survivor benefits flow to a defined set of relatives when a worker dies. Eligible recipients include the surviving spouse (or ex-spouse, if the marriage lasted at least ten years), unmarried children age 17 or younger (or up to 19 if still in school full-time), adult children who developed a disability before age 22, and dependent parents age 62 or older.6Social Security Administration. Who Can Get Survivor Benefits Under certain circumstances, stepchildren, adopted children, grandchildren, and stepgrandchildren also qualify.
The eligible list hugs the top of the consanguinity chart: spouse first, then first-degree lineal descendants, then first-degree lineal ancestors. Collateral relatives, including siblings, cousins, aunts, and uncles, are not eligible for Social Security survivor benefits regardless of how close they were to the deceased or how financially dependent they may have been.
What the Chart Doesn’t Cover
Consanguinity tracks blood only. Relationships created by marriage are called affinity: your spouse’s siblings, your siblings’ spouses, your parents-in-law. Affinity relatives do not appear on the consanguinity chart. Legal treatment of the two differs by context. Some states include affinity relatives in their marriage prohibitions; others restrict only blood ties. Federal nepotism law explicitly covers both, listing in-laws alongside blood relatives.
The distinction matters most in probate. Affinity relatives almost never inherit under intestate succession statutes. If your spouse dies and you later die without a will, your spouse’s siblings have no claim to your estate.
Proving the Relationship
Knowing where a person sits on your chart is one thing; proving it to a court or agency is another. The Social Security Administration, for example, accepts birth certificates, final adoption decrees, court paternity determinations, and foreign passports as evidence of a parent-child relationship.7Social Security Administration. Learn What Documents You Will Need to Get a Social Security Card Documents must be originals or copies certified by the issuing agency. Photocopies and notarized copies are not accepted.
When paper records are missing or disputed, DNA testing can fill the gap, but only if it follows strict chain-of-custody procedures: a neutral third party collects the samples, participants show government-issued ID and are photographed, everyone signs consent forms, and the lab holds accreditation from an organization like the AABB or meets CLIA standards. Home DNA kits bought online do not meet these requirements and carry no legal weight. Genetic evidence is strongest for close relationships where the expected shared DNA ranges don’t overlap much with other relationship types; for distant connections like second cousins, courts typically want DNA combined with traditional documentation such as vital records and family Bibles.