Guidelines for DNA Evidence of Siblings to Prove Relations

When U.S. citizens or lawful permanent residents petition for a family member, the proper relationship must be proven to USCIS. Absent primary evidence such as birth and marriage certificates, the parties may submit secondary evidence like affidavits, school records, and medical records. DNA testing can also supplement evidence, usually through establishing parent-child relationships. If someone petitions for their sibling, their familial relationship must be proven to USCIS.

A sibling relationship is defined in INA §§ 101(b)(1) and (2) as two people who are “children of at least one common parent”. Full siblings share both parents while half siblings share one parent. When it is not possible to test common parents, sibling DNA tests can be used. A newly released USCIS policy memo allows for use of DNA testing for sibling relationships and explains the guidelines.

Results are interpreted through percentage probability of a true relation. The accepted standard is 90 percent probability of familial relationship for both full and half siblings. Both half and full sibling tests are inconclusive when between 9 and 89 percent probability. Below 9 percent means the full-sibling relationship does not exist. For a half sibling test, below 9 percent is inconclusive. 

Test Result - percent probability of true relationship	Full Sibling Relationship	Half Sibling Relationship
90% and higher	Relationship Exists	Relationship Exists
9% – 89%	Inconclusive	Inconclusive
Below 9%	Relationship Does Not Exist	Inconclusive

Source: DNA Evidence of Sibling Relationships. Policy Memorandum. USCIS. April 17, 2018.


Inconclusive and exclusionary results do not mean the petition will be denied. It means that the relationship hasn’t been established but can still be accepted if sufficiently supported with other forms of evidence. If other submitted evidence is sufficient, the relationship can be accepted as true by USCIS anyway.

The type of test used can affect results and how they are judged. The above standards are based on testing 20 loci (genetic markers). Officers must tell petitioners that they can test more loci if the result was below 90 percent probability but tested less than 20 loci. AABB labs also updated their standards to test at least 20 loci when previous results were below 90 percent probability.

Testing against other relatives is also used to provide evidence of sibling relationships. The tested people do not have to be named on the petition. This provides more information to work with and is encouraged by AABB standards.

While DNA tests are powerful evidence, the results are not sole determinants in an application. Half and full sibling tests are suggested by USCIS as an alternative to unavailable primary evidence. Adjudicators look at the petition and all supporting documents as a whole. It is important that the petitioner prepare each part of the application carefully.