DNA tests for siblings and half-siblings are available online through vendors such as PaternityUSA.com, DNA-Paternity-testing.com and DNATCA.com. DNA sibling tests can establish paternity or maternity if the father or mother is not available to provide DNA for testing.
Sibling DNA test results are expressed in terms of the probability that two or more people are related as siblings or half-siblings or not related at all. Sibling DNA tests are not as conclusive as paternity or maternity DNA tests. Most tests are designed to test two putative siblings, but more siblings and sometimes the mother can be added to the tests for a higher fee.