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Family Finder

From ISOGG Wiki

The Family Finder is an Autosomal DNA test from Family Tree DNA that was first made available in February 2010.

Family Finder uses in excess of 700,000 Autosomal SNPs to help find relatives from all parts of one's family tree. Previously, DNA genealogy tests could only tell a person about a small part of their family tree based on DNA from the Y chromosome and mitochondria. By using Autosomal DNA (abbreviated as atDNA), Family Finder can trace any ancestral line, no matter where it is in the family tree. The test identifies matching segments of DNA. The size and number of shared segments will help to predict the possible relationship.

The science behind this involves comparing the atDNA of all participants to discover total Centimorgans (abbreviated as cMs) to determine up to and including 2nd cousins, then for 3rd cousin and higher they use largest cMs plus a formula to determine these as follows:

  • 1st longest block
  • 2nd longest block over 5
  • total of all cMs

on 500 SNPs or more.

To see some examples of Family Finder results for known close relationships see the screenshots in the separate article on Chromosome Browser Examples.

Steps to find your common ancestor for matches at Family Tree DNA


On your Personal Page in Family Finder, in the top bar under Family Finder, you will see the heading Matches. If you click on that it brings you to your Family Finder Matches page. You can sort your matches by the headings listed, for example Match Date to see your newest matches.

There are four useful icons under person's name. The first, an envelope, lets you email this person. The second, a dialogue icon, is for you to make notes about this person. The third, a family tree symbol, is green if they have uploaded their family tree. The last lets you choose to see all the matches in common with (or not in common with) this person.

Family Tree DNA has extensive help files. The page with help for the family finder matches page is:


There is a bar with more options for each match that you get by clicking the little arrow on the bottom left of the person (our hand drawn red arrow shows where that is). The bar is extended out in the person named Aunt M in aour example above.

When you receive a match in Family Finder, the first thing you must consider is the Suggested Relationship, as well as the Relationship Range. This gives you what the company feels your possible relationship is, with the Relationship Range giving you a range of where the actual relationship may be. Understand that relationships can also be outside of this range, as well, as testing autosomal DNA is not an exact science due to recombination.

Next look at the Shared cM (centimorgans) and Longest Block listed for the match. The combination of this information is what Family Tree DNA uses to determine your possible relationship. Another helpful tool on this page is the Ancestral Surnames. You can check your matches surnames to see if you may connect on a particular surname or surnames for further research.

Next view up to five of your matches in the Chromosome Browser. Do this by selecting Compare in Chromosome Browser on the bar below each person whose shared DNA segments you want to see. When you are done selecting use the big blue arrow at the top of the page to go to the chromosome browser.


You can select a single match under Filter Matches By… or up to five matches under Compare Genes. Once you make your selection(s), choose View This Data in a Table on the right side of the screen, and you will see the following information:


Start Location
End Location
Matching SNPs

This gives you the chromosome(s) where you match; the start and end locations for that match; the total cMs for that location, and how many Single-nucleotide polymorphisms (SNPs) matched. You will be looking for the longest block of cMs which, in this case, is 12.94 and any other blocks over 5.00. Using the longest block of cMs, you can use the following Match Outcomes list (below) to give you an idea of where your actual relationship may lie.

Match outcomes:

  • 10 cMs or higher indicates a match usually within 5 generations (4th or more recent cousins)* - better chance to find a match with a highly developed genealogy
  • 5-9 cMs can cover a range of 6 to 11 generations (5th to distant cousins)* – later generations may include low level matches that show you probably share a common ancestor but may not be able to effectively trace genealogically
  • Below 5 cMs (Mb) gives ancient ancestry

A generation can run an average of every 25–35 years. To understand generations and cousinship levels, check the following chart courtesy of Family Tree DNA's Learning Center.


These features can be found on your FTDNA personal page under User Preferences:

Personal Image: You have the option to insert a personal image or photo in your profile.

Ancestral Surnames: You have the option to list your Ancestral Surnames and Countries. List as many surnames from your genealogy as you can regardless of what generation they are in. Some matches have been made as far back as ten generations. List just the surname in the Surname field. Variant spellings should be listed as separate surnames. It is a good idea to list dates as well as locations in the Country field. Some people have listed the country with the state, county or province in parenthesis. Others have listed the county, province or state names first followed by the country with dates in brackets (see screenshot below). Avoid using abbreviations wherever possible. Remember that FTDNA has an international database. US state abbreviations for example will not be very familiar to your European matches.

After you have entered your ancestral surnames, you might notice that some of the ancestral surnames of your matches are highlighted in bold type, indicating that the highlighted surname might match one of yours. Note that Family Tree DNA is using a surname-matching algorithm that is somewhat liberal. For example, some pairs of surnames that it considers to be a potential match are BROWN and BRUN, NEELY and NEIL, PEGG and PIKE, and THORN and TRAHAN.

FF ancestral surnames.jpg

Inheritance patterns

Why is my relationship listed as 5th cousin to distant when I have a longest block over 10 cMs?

Family Finder uses a combination of the longest block of cMs and shared cMs to determine relationships. Sometimes there is a block larger than 10 cMs that is assigned a more distant relationship because of a smaller number of shared cMs. For example, you may have a match in Chromosome 5 that lists 15.31 cMs in the Longest Block, but only 27.93 in Shared cM. This is an anomaly. What happened is that cMs that we shared from our ancestors got broken down in all the other chromosomes except the one large block in Chromosome 5. This block should have broken down too but was in a place that did not recombine the same as the others. That is why FTDNA did not place it at a nearer cousinship. They usually place situations like these one cousinship back to distant.


For information on the methodology used to identify segments belonging to specific ancestors see the article A Methodology for Researching Autosomal DNA Results from Family Finder on the DNA Adoption website. See also the ISOGG Wiki articles on chromosome mapping, phasing and triangulation.

For advice on using the Family Finder "in common with" feature see the blog post by Judy Russell A common DNA question: FTDNA's "in common with" feature (The Legal Genealogist blog, 4 August 2013).

Population Finder

As an add-on to Family Finder, Family Tree DNA compares the DNA results with reference samples from several populations around the world and attempts to identify the sources of one's DNA on a continental level. Below are two examples, the first of which is for an individual whose DNA is estimated to be 97.07% European and 2.93% Native American.


The example below is for a child of the above example. The child is reported to be 98.25% European. The remaining 1.75% for the child is not reported as it likely falls below a confidence level for accurate assessment.


For an explanation of the workings of Population Finder and the meaning of the Middle Eastern percentages seen in many Population Finder results see the guest blog post by Doug McDonald on biogeograpical analysis.

See also Roberta Estes' blog post on the dreaded "Middle East" autosomal result.

Family Finder reviews

See also

External links