DNA Relationship Testing
A DNA relationship test can confirm that two people are related.
For example, an adoptee finds her presumed birth family. But the birth parent is not available for a paternity test. The adoptee can confirm the relationship by testing a potential half sibling.
That’s what I did in my own adoption search.
Another example occurs when a child’s alleged father dies without a paternity test. The man’s parents may wish to know if they are the child’s biological grandparents.
My Free Guide to DNA Testing
Before you dive into the details of this web site, I suggest you download my free Guide.
I describe and compare the major DNA test types. Then I explain their purposes, strengths and limitations in a unique table that you will not find anywhere else.
This Guide provides the high level overview you need to put the various DNA tests in perspective.
Just click the title below to reach the download page.
How to Identify Ancestors and Confirm Relationships through DNA Testing
There are two types of DNA relationship testing. Both methods depend on the principle that closely related people have more DNA in common than unrelated people.
DNA Kinship Testing
Also called sibling testing, this is the old-technology DNA test to show that two people are related.
The test compares two or more potential relatives by counting Short Tandem Repeats (STRs) on a small set of autosomal markers. Autosomal markers reflect the genetic contribution of both parents.
This form of DNA relationship testing cannot be as conclusive as a
That’s because there is no way to tell which marker value came from which parent.
At best, it can estimate the probability that two people have a given relationship. At worst, it can provide misleading results.
Now that better tests are available, I no longer recommend this type of test.
DNA Kinship Testing
for more about this type of test.
Autosomal DNA Testing
An alternative test type emerged in late 2009. That’s when 23andMe introduced their Relative Finder. Early in 2010 Family Tree DNA followed with their Family Finder.
Both are examples of
Autosomal DNA Testing.
This type of test (based on SNPs instead of STRs) is far more conclusive than traditional Kinship Testing. It checks more than 700,000 markers and actually MEASURES the amount of DNA that two people have in common.
No more guessing. No more results that just say "Maybe."
By measuring the number and length of common DNA segments, these tools can tell if you are full siblings, half siblings, first cousins etc.
Since you need to buy two tests for relationship testing, you will want to check these links for current prices on
and the test at 23andMe
See my page on
Relative Finder as a Kinship Test
for more details on this use of the 23andMe test.
Autosomal DNA Comparison
for a more detailed comparison of the two tests.
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