Skip to main content

Relationship testing

DNALabs can test for biological relationships to a legal standard. This legal standard is a legislative process that is outlined in the Family Law Regulations 1984.


DNA testing methods can provide information about relationships within a family. An analysis of whether two people (regardless of sex) are full or half siblings can be performed. However, unlike paternity testing, which provides very conclusive results, sibship analyses are not as conclusive. If two people are full siblings, mathematically we expect them to share 50% of the genetic markers we test. If two people are half siblings, then 25% of their genes will be common. This principle then allows us to determine statistically the chance that they would share the DNA if they are siblings, compared to if they are unrelated (ie. if they matched by chance - population frequency). It is not possible to determine with 100% certainty whether or not two people are siblings. These results are reported on a likelihood scale. It should also be considered that there is a chance of inconclusive results with this kind of testing.

Y Chromosome testing

Males have a single Y chromosome passed on from biological father to each son. The inheritance of the Y chromosome is strictly from male to male and will be shared by all male members of a common male predecessor, provided the male line is in place.

This testing can be used to establish if two men come from a common paternal line, which can include relationships such as siblings, uncle/nephew, cousins and many other possibilities. It should be noted that while this testing links back to a common line, it does not distinguish brothers from paternal cousins or sons from grandsons etc.

Samples from the different males are analysed at polymorphic sites and compared to distinguish whether the individuals share a paternal line (a common Y chromosome). 

Other combinations (Aunt/Uncle to Niece/Nephew or Grandparent to Grandchild)

Other family relationship and identification issues can be resolved using DNA identification technology. The reports issued for our relationship enquiries can support cases for deceased estates, Immigration applications and other legal matters where paternity or maternity testing may not be available. These results are reported on a likelihood scale. It should also be considered that there is a chance of inconclusive results with this kind of testing.

Who needs to be tested?

Each relationship enquiry is different and the testing may be determined by who is available to test. Our team will assist with your enquiry to determine the best test available to establish if a biological relationship exists.


Includes the following analysis for up to two donors: Sibship analysis, Y-Chromosome, Aunt/Uncle to Niece/Nephew, Grandparent to Grandchild

Relationship testing of two people $1,078 10-14 working days
Additional person in the same case $240 10-14 working days

More information

Relationship testing application form can be downloaded here or please contact us on 1300 663 244 or email to discuss your enquiry.