How 23andMe identifies your DNA Relatives

Scientific Details

Learn about your DNA Relatives, the diverse group of 23andMe customers who have DNA in common with you. Only individuals who have chosen to participate in DNA Relatives are the subject of this report.

How 23andMe identifies your DNA Relatives

To identify your DNA Relatives, we use an algorithm that finds segments of your DNA that are identical to DNA segments of other 23andMe customers. When these segments are sufficiently long, we infer that they were inherited from a recent common ancestor. These segments are known as “identical by descent,” or IBD. Our algorithm searches for these matches across virtually your entire genome, so we can identify DNA Relatives on any branch of your family tree.

Note: IBD/Half IBD:

The comparison results in this feature displays shared segments of DNA on separate lines representing each chromosome pair, and labels the shared segments as Half IBD, or identical by descent. Because you inherit one half of your DNA from your mother and the other half from your father, IBD segments typically occur on only a single chromosome. Half IBD refers to the amount of the genome in centiMorgans (cM) that contains an IBD segment on either chromosome. The percent DNA shared in DNA Relatives is based on this number.

Your half IBD and shared segments vary based on the closeness of your relationship with the matches with whom you are comparing. Closer relatives will share thousands of cM and many segments in common; more distant relatives may share only one. For some of your shares, if you connected outside of DNA Relatives, you may not share any segments at all.

Every time DNA is passed from one generation to the next, the two chromosomes in each pair are randomly shuffled with each other in a process called recombination. Then, only half of this new DNA ā€” one set of chromosomes ā€” is passed down to each child. The total amount of DNA passed down from an ancestor is cut approximately in half each generation. Through this process, long inherited segments are broken up generation by generation into multiple shorter ones and sometimes lost altogether.

Despite all of this generational shuffling, DNA Relatives is highly sensitive and can pick up matches ranging from siblings and uncles to distant eighth cousins ā€” individuals that share great-great-great-great-great-great-great grandparents with you. It may not always be obvious how you share a connection with someone, but that’s where our DNA Relatives tool comes in. Visit the tool to find out more about your matches and get in touch to learn about your family history.

See our Customer Care pages for more information:

Shared segments between cousins

Inheritance family tree graphic.

A closer look at the matching segment

An example graphic showing a matching segment between you and your cousin.

Sources of information used in this report

The Your DNA Family report provides aggregated summaries of several attributes of your DNA Relatives. The following information sources are used in the report:

Report Section
Source
Close to distant DNA Relatives

Computed IBD results from the DNA Relatives tool.

Locations of your DNA Relatives

Answers to survey questions by your DNA Relatives.

Ancestries of your DNA Relatives

Computed results from the Ancestry Composition report.

Traits and behaviors in your 23andMe DNA Family

Answers to survey questions by your DNA Relatives.

Traits in Your DNA Family

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