What Does an Avuncular DNA Test Prove? How Accurate Is It?

Avuncular DNA testing or aunt-uncle DNA testing is a way to figure out if a child is related to a potential aunt or uncle when the father isn't around for paternity testing.

This test works by comparing the child's DNA with that of the aunt or uncle, looking at specific genetic markers to see if they share a family connection.

While paternity testing is the best option for proving a child’s father, if the father is unavailable, establishing an aunt or uncle relationship may help confirm paternity.

When to Take an Avuncular DNA Test

An aunt or uncle DNA test or an avuncular DNA test is performed in place of a paternity test.

It is used when paternity needs to be confirmed, but the alleged child’s father is not available for testing.

The alleged father’s siblings can take his place during an avuncular test. It can determine paternity since siblings share 50% of their DNA.¹

A child shares roughly 25% of their genes with an uncle, but only if he is a full brother of the alleged father.

Who Takes an Avuncular Test? 

The following people are usually required to take an aunt/uncle DNA test:

• The child whose paternity needs to be proved
• The biological sister or brother of the alleged father
• The child’s biological mother (optional)

Some DNA testing companies include the child’s mother in the process. The mother’s genetic markers can help geneticists reach conclusive results since testing the mother ensures elimination of the similar genes acquired from her.

For better accuracy, it’s also best if more than one sibling takes the test.

What If the People Being Tested Are Both Males?

If the child and the alleged father’s sibling are biologically male, experts may perform a Y-chromosome DNA test for better accuracy.

This test is called Y-chromosomal short tandem repeat polymorphisms (Y-STR).

Fathers pass down their Y-chromosomes to their sons unchanged. Brothers will share the same Y-DNA from a common biological father.

A Y-STR test can tell if a male child and his alleged uncle share the same Y-DNA. It confirms that they are true biological relatives from the paternal side.²

How Aunt or Uncle DNA Testing Works

This is the most common process:

1. First, the lab experts will test DNA samples for a polymerase chain reaction (PCR). This process magnifies specific regions of the DNA and examines them for patterns. DNA patterns from the aunt or uncle’s samples are compared with the child and the biological mother.
2. The testing company will then generate a statistical analysis of genetic matches between the alleged aunt and niece or the uncle and nephew.
3. Next, the laboratory evaluates the gathered DNA samples from each subject and establishes a genetic profile. Genetic profiles are analyzed using a kinship index. A kinship index score of more than one suggests the subjects are likely to be related. Higher kinship index scores may indicate a closer biological relationship.

DNA Sample Collection for Avuncular Testing

Avuncular DNA tests use the same testing method as other DNA tests. DNA samples are collected from the insides of the cheek using a buccal swab.

The swab gently scrapes off cells from the mouth. You can collect the sample at home (with a self-collection kit) or with the help of a doctor.

Samples will be collected from each participant and sent to a laboratory for DNA analysis. The process usually takes a few days to a week. It depends on the testing company and its partner laboratory.

Benefits of Avuncular DNA Testing

Avuncular DNA testing offers some valuable benefits, especially when establishing a biological relationship is critical. These are:

• Father is unavailable – Aunt-uncle DNA testing can be used if the possible father is not available for paternity testing. This test gives an alternative way to establish biological relationships.
• Can address different needs – This test can help confirm family connections for personal knowledge, serve as legal proof, determine eligibility for social security benefits, support inheritance claims, and facilitate immigration or insurance matters.
• Provide clarity to complex family relationships – Avuncular DNA testing offers answers in complex family structures, especially if it involves half-siblings, uncles or aunts, nieces or nephews, and grandparents and grandchildren.
• Resolve uncertainties – If a paternity test is not possible, aunt-uncle DNA testing can be a way to get conclusive results, resolving uncertainties surrounding familial relationships.

Private vs. Legal Avuncular DNA Test

A private test may be enough if you want to confirm paternity for your personal knowledge or peace of mind. You can take these tests from the comfort of your home.

Avuncular DNA testing for legal purposes is usually done in an accredited laboratory, hospital, or clinic. However, some at-home DNA tests can give you court-admissible results.

Legal avuncular tests meet specific requirements. For example, they may:

• Include useful documents for third-party witnesses, like doctors or lawyers
• Undergo a chain of custody for witnessing and verification⁴

These ensure that the collected samples belong to the same people in the report. It prevents them from manipulating avuncular test results in their favor.