Grandparent DNA test

When the possible father can't take part, his parents can test with the child instead.

Used when
The possible father has died, can't be found or won't test
Who takes part
The child and the father's parents, and the mother if available
Clearest answer
Both of the father's parents
Samples
Cheek swabs
Court use
With a witnessed collection

How it works

A man gets half his DNA from his mother and half from his father. Together, his parents carry everything he could have passed to a child. The lab compares the child's markers with the grandparents' and reports how likely it is that their son is the father.

One grandparent or two?

  • Both of the father's parents: the clearest answer.
  • One grandparent: possible, but the result is weaker. The mother taking part helps.

Other relatives who can take part

If the grandparents can't take part, the father's full brother or sister can (aunt or uncle DNA test), or another child of his (sibling DNA test). See paternity tests without the father.

Questions

Can the grandparents test if the father is alive but refuses?

Yes, if they agree. Every adult tested gives their own consent.

Does the mother need to take part?

She doesn't have to, but her sample makes the result clearer.

Can it be used in court?

Yes, with a witnessed collection, as in a legal test.

Guides for this test

  • 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.
  • 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.
  • 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.

Other tests