5th Cousin: Who They Are, and Why Your DNA Usually Cannot See Them
A 5th cousin is someone who shares a set of great-great-great-great-grandparents with you, with each of you sitting exactly six generations below that couple. That is the entire definition, and it is the last cousin degree most people can name without counting on their fingers. The relationship is real, it is documented, and on a family tree it is perfectly precise. On a DNA test it is close to invisible: the majority of genuine fifth cousins share no detectable DNA with each other at all.
That gap between paper genealogy and genetic genealogy is what makes this degree worth its own page. A 5th cousin is a legitimate relative you can prove with records. It is also, statistically, a relative your test kit will probably never confirm.
Who Your Fifth Cousin Is
Your fifth cousin is a descendant of your 4x-great-grandparents, through a different child than the one you descend from, at the same generational distance as you.
Walk it slowly. Your 4x-great-grandparents had children. One of those children is your 3x-great-grandparent. Another of those children started a separate branch. Follow that second branch down through five more generations of births, and the person who arrives at your generation is your fifth cousin.
The counting rule behind it never changes:
- Cousin number = the number of generations from the closer person up to the shared ancestor, minus one
- Removals = the difference between the two people's generation counts
For a plain fifth cousin, both of you are six generations below the shared couple. Six minus one is five. The difference between six and six is zero, so there is no removal.
Because the relationship is symmetrical, both directions carry the same name. You are their fifth cousin, and they are yours. There is no senior or junior version of the term, and age has nothing to do with it. Your fifth cousin could easily be forty years older or younger than you, since branches of a family drift apart in timing across six generations of births.
The Common Ancestor, Degree by Degree
The pattern is completely regular once you see it laid out. Every cousin degree pushes the shared ancestor exactly one generation further back.
| Cousin degree | Shared ancestors | Generations each of you is below them |
|---|---|---|
| 1st cousin | Grandparents | 2 |
| 2nd cousin | Great-grandparents | 3 |
| 3rd cousin | 2x-great-grandparents | 4 |
| 4th cousin | 3x-great-grandparents | 5 |
| 5th cousin | 4x-great-grandparents | 6 |
| 6th cousin | 5x-great-grandparents | 7 |
Nothing about the side of the family enters into this. A fifth cousin who reaches you through your mother and one who reaches you through your father get the identical label, for the reasons laid out in what is your mother's cousin to you.
Your 4x-great-grandparents were probably born somewhere in the first half of the 1800s, give or take a few decades depending on how young or old people in your family tended to be when they had children. That places the connection point in an era of census records, church registers, and land deeds, which is exactly why fifth cousins are findable on paper even when they are unfindable in your DNA.
If you would rather not count generations by hand, the free relationship calculator at cousinchart.com takes two people and returns the exact term, removals included.
How Much DNA a 5th Cousin Shares
Two fifth cousins are expected to share about 0.05% of their DNA, which works out to roughly 3 to 4 centimorgans. In practice, most fifth cousin pairs share nothing a testing company can see.
Those two sentences need unpacking, because the numbers people quote for this degree are genuinely misleading if you do not know where they come from.
The theoretical expectation. Cousin relationships halve in expected sharing at each step. First cousins average about 12.5%, second cousins about 3.125%, third cousins about 0.78%, fourth cousins about 0.195%, and fifth cousins about 0.0488%. Against a total autosomal genome of roughly 6,800 to 7,400 cM depending on which company measures it, 0.0488% lands at about 3.4 cM.
The detection threshold. Consumer DNA tests generally do not report segments below about 6 to 8 cM, because shorter matches are so often false. So the expected sharing for a fifth cousin sits below the floor of what gets reported. That is not a flaw in the tests. It is what happens when you cut the shared inheritance in half eleven times.
The observed range. Among fifth cousin pairs where DNA is detected, community datasets like the Shared cM Project report an average around 25 cM and a range running from 0 up to somewhere near 120 cM. Treat both ends of that as soft. These are crowd-submitted figures from real testers, and the sample is small at this distance.
Here is how the degree sits next to its neighbors. Every number below is an average that varies enormously from pair to pair:
| Relationship | Expected shared DNA | Typical reported range | Odds of detectable DNA |
|---|---|---|---|
| 3rd cousin | ~0.78% | roughly 0–220 cM | ~90% |
| 4th cousin | ~0.195% | roughly 0–140 cM | ~45–50% |
| 5th cousin | ~0.05% | roughly 0–120 cM | ~10–15% |
| 6th cousin | ~0.012% | roughly 0–70 cM | under 10% |
The last column is the one that matters. Roughly 85 to 90 percent of true fifth cousins share no detectable DNA whatsoever. They are still related. The DNA just did not survive the trip.
Why the Reported Average Is Misleading
The 25 cM average for fifth cousins is calculated only from pairs who found each other, which means it systematically excludes everyone who shares nothing.
This is a selection effect, and it is severe at distant degrees. To submit a fifth cousin pair to a shared-DNA database, you must first be matched, which requires shared DNA above the threshold. The thousands of fifth cousin pairs sharing zero centimorgans never enter the dataset because neither person ever knew the other existed.
So the honest way to read the number is: if two fifth cousins show up as matches at all, they will typically share somewhere in the 10 to 40 cM range. The true average across all fifth cousin pairs, including the invisible ones, is closer to that 3 to 4 cM theoretical figure, and for most individual pairs the real answer is a flat zero.
Anyone quoting a single confident number for fifth cousin DNA without mentioning this is quoting it wrong.
How Many 5th Cousins Do You Have?
Somewhere in the thousands to tens of thousands, with estimates commonly landing in the ten to twenty thousand range.
The math is straightforward in principle and hopeless in practice. You have 64 4x-great-grandparents on paper, or 32 ancestral couples. Each of those couples had children, and each of those children's lines branched again through six generations. Multiply average family sizes through those generations and the count explodes.
Two things pull the real number down. First, pedigree collapse: at this depth, some of those 64 ancestral slots are filled by the same people twice, because distant cousins married each other at some point in your family's past. This happens in essentially every family tree and is completely ordinary. Second, family sizes vary wildly by era and region.
The practical takeaway is that fifth cousins are not rare or special. You have a stadium's worth of them, most live within a few hundred miles of where your ancestors settled, and you have almost certainly stood in line behind one at a grocery store.
How a Fifth Cousin Shows Up in a DNA Match List
Almost never by name. When one does appear, the testing company will not call it a fifth cousin.
Here is what to actually expect:
The label will be a range, not a degree. Ancestry typically shows something like "4th–6th cousin" or files the match under "Distant Cousins." 23andMe tends toward "4th cousin" or "5th cousin or further." MyHeritage and Family Tree DNA use similarly wide bands. None of these are claims about the specific relationship; they are the company's best guess from a shared centimorgan total, and at this level the guess covers a dozen possible relationships.
The shared total will be small and singular. A detected fifth cousin usually shows up as one segment somewhere in the 7 to 25 cM range. Two shared segments at this distance is uncommon. A single small segment carries very little information on its own.
It will be indistinguishable from other relationships. A 15 cM match could be a fifth cousin, a fourth cousin twice removed, a sixth cousin who got lucky, or a false positive from a stretch of DNA that is common in your population. The centimorgan number alone cannot separate these. This is the opposite of what happens at closer degrees, where the shorthand notations covered in abbreviation for cousin map fairly cleanly onto DNA ranges.
Trees do the work, not the DNA. The only way to confirm a fifth cousin is to find the shared 4x-great-grandparent couple in documented records. The DNA match is a hint that tells you where to look. It is not evidence of the relationship by itself.
Endogamy Breaks These Numbers Completely
In populations where distant cousins have married each other for generations, fifth cousin matches share far more DNA than the tables predict, and the tables should not be used.
Ashkenazi Jewish, Acadian and Cajun, Low German Mennonite, Polynesian, and many island and isolated rural populations all show this pattern. In an endogamous community, two people are related to each other through many different lines at once, not one. All those tiny contributions add up, so a documented fifth cousin might share 60 or 80 cM, a total that would suggest a third cousin in a non-endogamous family.
If your family comes from a community like this, standard shared-cM charts will consistently make your matches look closer than they are. Use tools built for endogamous populations, and lean much harder on documented trees than on centimorgan totals.
Fifth Cousin Once and Twice Removed
Your fifth cousin's child is your fifth cousin once removed. Your fifth cousin's grandchild is your fifth cousin twice removed.
Removals count generational distance and do nothing to the cousin number. The same logic that makes your parent's first cousin your first cousin once removed applies unchanged out here at the fifth degree. The full treatment of that mechanism is in 1st cousin 2x removed and 2nd cousin 1x removed, both of which explain how removal is counted and how it shows up in DNA numbers.
Expected DNA drops with each removal, so a fifth cousin once removed averages roughly half what a fifth cousin does, and a fifth cousin twice removed roughly a quarter. At numbers this small, all three relationships are effectively equivalent from a testing standpoint: probably zero, occasionally a small segment.
Are Fifth Cousin Matches Worth Anything?
Individually, rarely. In clusters, sometimes a great deal.
A single distant match with no tree attached is not worth chasing. But ten distant matches who all descend from the same 4x-great-grandparent couple are strong collective evidence, even though no single one of them proves anything. Clustering tools that group your matches by shared segments turn a pile of unusable fifth cousins into a usable signal about one specific ancestral line.
They are also genuinely useful when you already have a hypothesis. If records suggest your 4x-great-grandfather had a brother who moved west, and you find three small matches descending from that brother, the DNA supports what the paper trail already suggested. That is the correct way to use a fifth cousin match: as confirmation of research, not as a starting point for it.
And if a fifth cousin does reach out and you both have decent trees, the connection can be delightful. Families at this distance often hold photographs, letters, and stories that your branch lost generations ago. In many families, especially where the term "cousin brother" is used the way described in cousin bro, these wide connections stay socially warm regardless of what a centimorgan chart says about them.
Frequently Asked Questions
How much DNA do 5th cousins share?
About 0.05% on average, roughly 3 to 4 centimorgans, which is below what testing companies report. Among fifth cousin pairs that do show up as matches, the shared amount typically falls between about 10 and 40 cM. All of these figures are averages that vary widely between individual pairs.
Can 5th cousins share no DNA at all?
Yes, and most of them do. Roughly 85 to 90 percent of genuine fifth cousins share no detectable DNA with each other. Sharing nothing is the normal outcome at this degree, not evidence that the documented relationship is wrong.
What ancestor do 5th cousins share?
A set of great-great-great-great-grandparents, usually written as 4x-great-grandparents. Each fifth cousin is six generations below that couple.
Is a fifth cousin actually related to you?
Yes. The relationship is documented and real, and a shared 4x-great-grandparent is a genuine genealogical connection. It is simply distant enough that the genetic evidence usually washes out.
Why does my DNA test call someone a 5th cousin when we cannot find the link?
Because the label is an estimate from a centimorgan total, not a determination of the relationship. A match reported as a fifth cousin might be a fourth cousin twice removed, a sixth cousin, or occasionally a false positive. Wide prediction ranges at this distance are expected.
Can 5th cousins marry?
Yes, everywhere. No jurisdiction in the United States or in any country regulates marriage at anything close to the fifth cousin level, and the shared ancestry involved is negligible.