What states can 3rd cousins marry?
According to the NCSL, cousin marriage is legal in: Alabama, Alaska, California, Colorado, Connecticut, District of Columbia, Florida, Georgia, Hawaii, Maryland, Massachusetts, New Jersey, New Mexico, New York, North Carolina (in North Carolina, first-cousin marriage is legal, but double-cousin marriage is prohibited), ...
In short, yes, it is legal for second and third cousins to marry in the US. Beyong that, state laws get a little more complicated. According to the National Conference of State Legislatures: "Twenty-five states prohibit marriages between first cousins.
It's legal in all 50 states to marry a cousin who's your second cousin or further. But according to a new study out of the University of Iceland in Reykjavik, it's not just legal, it's smart.
State | First cousin marriage allowed | Adopted-cousin marriage allowed |
---|---|---|
Alaska | No | Yes |
Arizona | Only if both parties are 65 or older, or one is infertile | Yes |
Arkansas | No | Unknown |
California | Yes | Yes |
The researchers suggest marrying third and fourth cousins is so optimal for reproduction because they sort of have the "best of both worlds." While first-cousin couples could have inbreeding problems, couples who are far-removed from each other could have genetic incompatibilities.
First cousins share a grandparent (2 generations) Second cousins share a great-grandparent (3 generations) Third cousins share a great-great-grandparent(4 generations)
First cousins share 12.5%, second cousins 3.125%, third cousins 0.78125%, and so on. But in real life, these are averages. The exact numbers will vary, sometimes a lot. In this figure, the amount of shared DNA is expressed in something called centimorgans (cM).
In the United States, second cousins are legally allowed to marry in every state. However, marriage between first cousins is legal in only about half of the American states. All in all, marrying your cousin or half-sibling will largely depend on the laws where you live and personal and/or cultural beliefs.
2 (1) Subject to subsection (2), persons related by consanguinity, affinity or adoption are not prohibited from marrying each other by reason only of their relationship. (2) No person shall marry another person if they are related lineally, or as brother or sister or half-brother or half-sister, including by adoption.
Third cousins are not technically considered to be distant relatives. A distant relative is someone who is more distantly related than a third cousin. By definition, a third cousin is not a distant cousin. All of our cousins who are related to us at a third cousin distance or closer are defined as close cousins.
What happens if you date your third cousin?
There's no danger in marrying your third cousin — and actually genetic tests are a good idea for ANY marriage since even unrelated people can both be carriers of dangerous traits.
Alabama Marriage Requirements
You cannot marry children, siblings, parents, uncles, aunts, grandchildren, grandparents or great grandparents of any relation. You can marry first cousins without restriction, however.

Edgar Allan Poe.
For his second marriage, the famed poet and author of “The Raven” wed his first cousin Virginia Eliza Clemm. The two were married when he was 27 and she was 13.
Twenty-four states prohibit marriages between first cousins. Twenty states and the District of Columbia allow cousins to marry; six states permit first-cousin marriage only under certain circumstances.
Your children and your third cousin's children would be fourth cousins. In most cases, your third cousin has a great-grandparent whose sibling is your great-grandparent. Thus, you and your third cousin share a set of great-great-grandparents.
...
Percent DNA Shared by Relationship.
Relationship | Average % DNA Shared | Range |
---|---|---|
2nd Cousin once removed | 1.5% | 0.57% - 2.54% |
3rd Cousin | 0.78% | 0.3% - 2.0% |
Must first cousins be forbidden to marry? In the Bible, and in many parts of the world, the answer is no. But the answer is yes in much of church law and in half the United States.
Relationship | Average % DNA Shared | Range |
---|---|---|
1st Cousin once removed Half first cousin | 6.25% | 2% - 11.5% |
2nd Cousin | 3.13% | 2% - 6% |
2nd Cousin once removed Half second cousin | 1.5% | 0.6% - 2.5% |
3rd Cousin | 0.78% | 0% - 2.2% |
- Husband, wife or civil partner (including cohabitee for more than 6 months).
- Son or daughter.
- Father or mother (an unmarried father must have parental responsibility in order to be nearest relative)
- Brother or sister.
- Grandparent.
- Grandchild.
- Uncle or aunt.
- Nephew or niece.
Relationship | Number of cousins |
---|---|
Third cousins | 175 |
Fourth cousins | 1,570 |
Fifth cousins | 17,300 |
Sixth cousins | 174,000 |
Are 5th cousins blood-related?
Are Fifth Cousins Blood-Related? Fifth cousins are related, but there is a chance they do not share DNA. In fact, there is only a 10-15% chance of sharing genetics with any fifth cousin. Even if you and our fifth cousin are related by blood, the DNA shared will be small, especially when compared to closer cousins.
Are fourth cousins blood-related? Because you only share DNA with around half of your fourth cousins, there is a chance that you are not “blood-related.”
What Is a Cousin? Cousins are people who share a common ancestor that is at least 2 generations away, such as a grandparent or great-grandparent. You and your siblings are not cousins because your parents are only 1 generation away from you.
What is a third cousin? Your third cousin is a person with whom you share a great-great-grandparent.
Christianity as a whole has no rules against marriages among cousins. It's actually looked on favorably in the Old Testament and it is not mentioned in the New Testament. Some church's, such as the Roman Catholic Church, have guidelines against marriages to close relatives.
Marriage between cousins is a contentious topic across the globe, but you may be surprised to hear it's completely legal in the UK.
Types of First Cousins
While ortho-cousins (also called parallel cousins) are children of two brothers or two sisters; cross-cousins are children of a sister and brother.
Because many cases are not reported it is difficult to say what the exact numbers are. However, according to reports, Florida has the highest incest rate in the country. The second highest rate is in the state of Alaska.
(1) No marriage shall be contracted between persons who are nearer of kin to each other by consanguinity, whether of the whole or half-blood, than second cousins. (2) Marriages prohibited by subsection (1) of this section are incestuous and void. History: Amended 1946 Ky.
Future president Franklin Delano Roosevelt weds his fifth cousin once removed, Eleanor Roosevelt, in New York on March 17, 1905.
Which president married his first cousin?
Intermarriage skipped a generation with John Quincy Adams, who married a non-relative. But, at 25 years old, John Quincy's second-eldest son, John, married his first cousin on his mother's side, 22-year-old Mary Catherine Hellen, in a private ceremony at the White House.
cousin-in-law (plural cousins-in-law)
In 1858, Kansas became the first state to prohibit cousin marriage. Before 1930, twenty-eight states passed a cousin ban. Only three states have taken prohibitory action in the last century: Kentucky (1946), Maine (1985), and Texas (2005).
A double cousin occurs when two siblings from one family marry two siblings from another family and both couples have children. Those children are first cousins to one another twice over, through both of their parents.
double cousin (plural double cousins) A cousin who is related on both sides of a family. A relative with four common grandparents.
And though it will increase your chances of birthing a healthy baby, it is a bit unorthodox, to say the least. Still, scientists at Icelandic biotechnology company deCODE genetics say that when third and fourth cousins procreate, they generally have scads of kids and grandkids (relative to everyone else).
Are fourth cousins blood-related? Because you only share DNA with around half of your fourth cousins, there is a chance that you are not “blood-related.”
So, to you, your third cousin's child would be your third cousin once removed. Your third cousin, to your parents, would be their second cousin once removed.
Are Fifth Cousins Blood-Related? Fifth cousins are related, but there is a chance they do not share DNA. In fact, there is only a 10-15% chance of sharing genetics with any fifth cousin. Even if you and our fifth cousin are related by blood, the DNA shared will be small, especially when compared to closer cousins.
If first cousins have children, the children are second cousins to each other. They're the same generation as each other, because they share a set of great-grandparents. If second cousins have children, the children are third cousins to each other.
How many 3rd cousins does the average person have?
Erlich explains that, on average, a person has around 850 relatives who are third cousins or closer relations. (Consider what a third cousin is: These are relatives you share a great-great-grandparent in common with. It can be a lot of people!).
...
Percent DNA Shared by Relationship.
Relationship | Average % DNA Shared | Range |
---|---|---|
2nd Cousin once removed | 1.5% | 0.57% - 2.54% |
3rd Cousin | 0.78% | 0.3% - 2.0% |
4th Cousin | 0.20% | 0.07% - 0.5% |
5th Cousin | 0.05% | Variable |
If people in this population meet and breed at random, it turns out that you only need to go back an average of 20 generations before you find an individual who is a common ancestor of everyone in the population.
If your aunt married a man who had a child from their prior relationship then you may call this child your cousin and grow up knowing them as your cousin, but they are not blood relatives. The amount of DNA that first cousins share can vary from around 7% to 13.8%. On average, first cousins share around 12.5% DNA.
Are second cousins blood-related? As the children of first cousins, second cousins are blood-related. Second cousins share great-grandparents and as first cousins share grandparents, the connection is halved with every new generation.
References
- https://www.quora.com/Can-you-go-out-with-your-3rd-cousin
- https://www.thetech.org/ask-a-geneticist/can-you-marry-cousin
- https://www.brainerddispatch.com/lifestyle/many-church-laws-but-not-the-bible-prohibit-first-cousin-marriages
- https://www.vox.com/science-and-health/2018/10/12/17957268/science-ancestry-dna-privacy
- https://www.history.com/this-day-in-history/franklin-roosevelt-marries-eleanor-roosevelt
- https://thednageek.com/double-cousins-and-dna/
- https://whoareyoumadeof.com/blog/what-is-a-third-cousin/
- https://www.genealogyexplained.com/what-is-a-first-cousin/
- https://www.bbc.com/news/magazine-19331938
- https://www.thetech.org/ask-a-geneticist/lannister-genetics
- https://www.marham.pk/healthblog/cousin-marriage-problems-2/
- https://www.thetech.org/ask-a-geneticist/third-and-fifth-cousins-dna-tests
- https://www.findlaw.com/legalblogs/law-and-life/is-it-illegal-to-marry-a-third-cousin/
- https://apps.legislature.ky.gov/law/statutes/statute.aspx?id=36465
- https://customercare.23andme.com/hc/en-us/articles/212170668-Average-Percent-DNA-Shared-Between-Relatives
- https://11points.com/marry-third-cousin/
- https://www.quora.com/Can-I-marry-my-cousin-in-Christianity
- https://support.ancestry.com/s/article/Understanding-Kinship-Terms?language=en_US
- https://www.familysearch.org/en/blog/cousin-chart
- https://www.somersetlive.co.uk/news/its-legal-marry-your-cousin-2637895
- https://www.genealogyexplained.com/what-is-a-second-cousin/
- https://www.law.cornell.edu/wex/incest
- https://homework.study.com/explanation/what-state-has-the-highest-incest-rate.html
- https://www.lawinfo.com/resources/family-law/alabama/
- https://www.thehealthyjournal.com/faq/do-cousins-get-attracted-to-each-other
- https://www.genealogyexplained.com/what-is-a-fifth-cousin/
- https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/inbreeding
- https://brownmath.com/general/relation.htm
- https://www.scientificamerican.com/article/when-incest-is-best-kissi/
- https://www.mind.org.uk/information-support/legal-rights/nearest-relative/about-the-nearest-relative/
- https://www.genealogyexplained.com/what-is-a-third-cousin/
- https://en.wikipedia.org/wiki/Cousin_marriage_law_in_the_United_States
- http://gap.med.miami.edu/learn-about-genetics/have-questions-about-genetics/if-cousins-get-married-are-they-at-risk-of-having-children-with-genetic-con
- https://en.wiktionary.org/wiki/double_cousin
- https://laws-lois.justice.gc.ca/eng/acts/M-2.1/page-1.html
- https://www.history.com/this-day-in-history/john-quincy-adams-son-marries-relative-at-the-white-house
- https://en.wiktionary.org/wiki/cousin-in-law
- https://www.oprah.com/relationships/keeping-marriage-in-the-family
- http://services.dpw.state.pa.us/oimpolicymanuals/ltc/Popups/blood_relative.htm
- https://isogg.org/wiki/Cousin_statistics
- https://www.discovermagazine.com/health/cousin-marriages-may-be-taboo-but-theyre-not-genetic-disasters
- https://education.myheritage.com/article/how-many-times-removed-untangling-distant-family-relationships/
- https://www.thehealthyjournal.com/faq/can-you-marry-your-cousin-and-have-a-baby
- https://www.thehealthyjournal.com/faq/at-what-point-are-cousins-not-related
- https://www.genealogyexplained.com/what-is-a-fourth-cousin/
- https://cardozolawreview.com/the-unconstitutionality-of-state-bans-on-marriage-between-first-cousins/
- https://blogs.ancestry.com/cm/9-famous-people-who-married-their-cousins/
- https://en.wikipedia.org/wiki/Cousin_marriage
- https://customercare.23andme.com/hc/en-us/articles/212170958-DNA-Relatives-Detecting-Relatives-and-Predicting-Relationships
- https://www.washingtonpost.com/wp-srv/metro/daily/graphics/cousins_042505.html?noredirect=on
- https://fivethirtyeight.com/features/how-many-americans-are-married-to-their-cousins/
- https://www.livescience.com/2271-kissing-cousins-kids.html