Overview
What Is the Siblingship Test?
The Siblingship Test determines whether two alleged siblings share the same biological father. It is most commonly used when a direct paternity test is not possible — for example, when the alleged father is unavailable or deceased.
Results are expressed as a likelihood index (kinship index). This test can be performed for personal or legal purposes.
Test Types
Full vs. Half Siblingship
Choose the type of siblingship test based on the relationship between the alleged siblings.
Full Siblingship
Same Mother, Possible Same Father
Used when two alleged siblings share the same biological mother, and the question is whether they also share the same biological father. The shared mother’s contribution can be accounted for, increasing result confidence.
Half Siblingship
Different Mothers, Possible Same Father
Used when two alleged siblings do not share the same biological mother, but may share the same biological father. Both mothers’ participation is strongly encouraged to improve accuracy.
Participation & Results
How the Test Works
Who Should Participate
For the most conclusive results, all available related parties should be included.
- Both alleged siblings must participate — no more than two at a time.
- Mother(s) are strongly encouraged to participate — their inclusion greatly improves accuracy.
- If the mother is unavailable, the test can still be performed but results may be less conclusive.
Turnaround & Format
Results are available in 3–5 working days from receipt of samples.
The test is available for both personal and legal purposes. Legal testing requires collection at an authorized site with chain-of-custody documentation.
Interpreting Results
Understanding the Likelihood Index
The siblingship test produces a likelihood ratio (kinship index) rather than a definitive yes/no answer. Note that results are generally less conclusive than direct paternity or maternity tests.