Using a DNA test, you can determine if a person is a second cousin by the percentage of DNA that is shared between two people and compare it with known ranges of cousins. This provides a scientific answer, instead of family guesswork. Relationship DNA testing has become more accessible and more accurate than ever to find second cousins and other distant relatives, whether you are creating a family tree, looking to find biological relatives or simply curious if you have one. This blog illustrates how it works.
Can a DNA Test Identify a Second Cousin?
Yes, a set of relatives can be used for a DNA test, as it measures the percentage of DNA that two people share and then compares that percent to ranges for various familial relationships. Second cousins have enough predictable amount of genetic material that makes it possible to identify the relationship with reasonable certainty in the lab. The outcome of the test is not always conclusive on its own, but it can serve as a solid, scientific basis for confirming or further researching a prospective second cousin match, when coupled with the family tree data.
How Shared DNA Reveals Family Relationships
DNA test for relatives is based on comparison of genetic profiles, and the amount of DNA shared between two people (in centimorgans) is compared to specific relationship categories based on known genetic inheritance patterns.
Relationship DNA testing is a starting point for identification because second cousins share a predictable DNA range compared to more distant cousins, third cousins.
What percentage of DNA do second cousins share?
According to the International Society of Genetic Genealogy and their autosomal DNA statistics (https://isogg.org/wiki/Autosomal_DNA_statistics), second cousins on average share 212.5 centiMorgans (cMs), but in extreme cases can actually share as little as 47 cMs or as much as 760 cMs. To understand what a second cousin DNA test for relatives this range, and the genetic reason why, consider that second cousins share one set of great-grandparents, meaning that the shared DNA can differ significantly from one pair to the next, depending on the natural randomness of genetic inheritance.
Knowing about Shared DNA, Centimorgans and Relationship Ranges
Centimorgans is a measure of how much DNA two individuals share. Second cousins share an average of about 47 to 212 centimorgans, but this is somewhat variable due to the randomness of genetic inheritance at each generation. The overlap with the other relationship categories is why family tree context is always recommended as well as raw DNA matching data, for accurate relationship confirmation.
Which type of DNA test is best to use when searching for a second cousin?
A second cousin relationship falls well within the range that autosomal DNA testing can reliably detect, making it one of the best-suited relationships to confirm using this method. It is carried out on DNA inherited from both sides of the family across all of the chromosomes.
Autosomal testing, Y-DNA testing, and other testing options compared.
- Autosomal DNA testing is the most convenient and common DNA test to use when looking for relatives up to about 5 to 6 generations away and compares DNA from all the non-sex chromosomes.
- It is important to note that Y-DNA testing can only be used to identify direct paternal lines and is not helpful for identifying maternal second cousins unless both people are from the same continuous line of descent. In other words, Y-DNA requires both cousins to be from the same direct male line, the results will be more accurate even if the two second cousins are born 50 years apart.
- mtDNA testing only goes back directly through females likewise, second cousins will only match in the event that they have a shared common female ancestor in their family history with no missing females in the direct maternal line.
How to Distinguish a Second Cousin from another Possible Relative?
Because the range of centimorgan similarity between second cousins and other types of cousins with similar DNA is overlapping, it is necessary to combine the raw DNA match data with other tools to distinguish a second cousin match from other types of similar match.
Using Shared DNA, Family Trees, and Genetic Matches
These two factors, centimorgan measurement and family tree comparison and shared match analysis (which other family members do both people share) all contribute to accurate second cousin identification. If two people have common great-grandparents that can be confirmed by tree research and their DNA matches are considered to be within the second cousin range, the relationship is much more likely to be confirmed and more confidence is given in the identification.
Choice DNA has been working with CLIA-accredited laboratories to offer professional relationship DNA testing services, Y DNA testing, a range of DNA testing services for personal and lawful uses and autosomal DNA testing for cousin and family identification, paternity DNA testing, etc. From determining what constitutes a second cousin relationship based on genetic matching, or verifying a closer relationship, Choice DNA consistently provides accurate, professionally processed results, with documentation and laboratory grade precision.
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Conclusion
When you know what the numbers mean and how to combine them with family tree research, it’s easy to find a second cousin by DNA testing. Relationship DNA testing eliminates guesswork, and science takes its place. Choice DNA offers professional and CLIA-accredited DNA testing services for all families, the correct and reliable answers they are looking for. Seek professional assistance family relationships are bigger than an educated guess.
