Can you do a paternity test without the father?

Yes: a lab can compare the child's DNA with the possible father's close relatives, and testing both of his parents gives the clearest answer. If he has died, a stored sample held by a medical facility, coroner or medical examiner may also work.

Updated November 14, 2026

When the possible father can't take part, labs can test his biological relatives instead. Cleveland Clinic lists his parents, grandparents, aunts, uncles and siblings as options, because close relatives share a lot of the same DNA. These relationship tests give a probability that the child and the relatives are related as claimed. Closer relatives give clearer answers, and testing more of them, plus the child's mother, makes the result stronger. Our guide to reading paternity test results explains how these probabilities work.

Can a grandparent do a paternity test?

Yes. A grandparent DNA test compares the child with the possible father's parents. Every part of the father's DNA came from his two parents, so testing both of them gives the clearest result. DNA Diagnostics Center (DDC) recommends testing both paternal grandparents, and the child's mother, where possible. One grandparent can test alone, but DDC says the result may be less conclusive. DDC reports a probability of relationship and treats 90.9% or higher as supporting the relationship.

Siblings and half siblings

If the possible father has other children, a sibling DNA test can compare them with the child. The report shows whether the two are likely half siblings, full siblings or unrelated. Sibling results are often less clear-cut than parent tests. The State Department notes that real siblings can score below 90%, and DDC treats results between 9.09% and 90.9% as inconclusive, meaning more people need to be tested. Testing each child's mother helps the lab see which DNA came from the father's side.

If both children are male, a Y-chromosome test is another option. The Y chromosome passes from father to son, so two males with the same father share it. It can't show which man in a family is the father, though, because men in the same direct male line, such as brothers, usually carry the same Y chromosome.

Aunts and uncles

The possible father's brothers and sisters can take an aunt or uncle DNA test. According to DDC, aunts and uncles share about 25% of their DNA with a niece or nephew, so results are weaker than with grandparents. The State Department doesn't recommend aunt or uncle tests in visa cases, because they can't reach its 99.5% standard. Testing more relatives helps.

Paternity test with a deceased father

If he has died, there are three places to look.

  • A stored sample. Cleveland Clinic says you may be able to get a sample from a medical facility, coroner's office or medical examiner's office. Morticians sometimes make a blood card when they handle a body. Labcorp notes that using a deceased person's sample can take coordination between several agencies.
  • Personal items. Labs can sometimes test items such as a toothbrush or hair, and DDC says used tissues or ear swabs work better. Success varies. Because no one can prove whose item it was, these results don't meet the chain-of-custody standard a legal test needs. Ask the lab what authorization it needs before sending anything.
  • His relatives. His parents, brothers and sisters, or other children can be tested as described above.

Where relatives disagree or an inheritance is at stake, a court can order testing. In Texas, for example, a court may order genetic testing of a deceased person for good cause, and it can order his parents, siblings and other children to give samples if his own isn't available. DDC says a medical examiner usually collects the sample under a court order, and in some cases a court orders exhumation. If an inheritance or benefits claim depends on the result, ask a lawyer in your state which test the court or agency will accept.

Can you do a paternity test without the mother?

Yes. A standard paternity test works with just the child and the possible father. Labcorp says it prefers to include the mother when possible, and Genetrack says a test without her can still be conclusive. Her sample matters more when the father isn't tested. In grandparent, sibling and aunt or uncle tests, it helps the lab work out which half of the child's DNA came from the father's side.

Everyone tested must agree

Each adult gives their own consent, and a parent or legal guardian consents for a child. Testing a living man's DNA from his belongings without his agreement isn't an option. In Florida, for example, submitting another person's DNA for analysis without express consent is a felony under section 817.5655 of the Florida Statutes.

If the possible father's parents are willing to take part, our grandparent DNA test is the natural next step. Our sibling DNA test and aunt and uncle DNA test cover the other relatives.

Questions

Is a grandparent DNA test as accurate as a paternity test?

Testing both paternal grandparents and the mother gives the strongest result. With one grandparent, DDC says the result may be less conclusive.

Can I do a paternity test if the father refuses?

Not with his DNA unless he agrees or a court orders it. In a paternity or child support case, a court or your state child support agency can order testing. See court ordered paternity tests. His relatives can also choose to take part.

Can a paternity test be done with the father's brother?

Yes, through an uncle test, though the result is weaker than a grandparent test. Testing more relatives, and the child's mother, makes it stronger.

Sources

Related guides

  • How do you read paternity test results?Look first at the probability of paternity and the conclusion. A result of 0% means the man tested is excluded as the biological father; 99% or more, backed by a large combined paternity index, means he is very likely the father.
  • Can a paternity test be wrong?Rarely, and most often because of a sample problem, such as a mix-up or contamination, or because the man tested is closely related to the real father. Identical twins are the one case a standard test can't settle.
  • How do you get a court ordered paternity test?Ask the judge in your paternity, custody or support case, or your state's child support agency, to order genetic testing. If both parents agree to test, you don't need an order: a private legal test uses the same chain-of-custody collection.