What Is Sibling DNA Test?
A sibling DNA test examines whether two or more people are biological siblings.
The test identifies whether they share both parents or one in common.
However, it is not as effective as paternity or maternity tests; it is helpful when the alleged parents (genetic parents) are unavailable for testing.
It relies on a statistical probability to compare the DNA of potential siblings.
It determines the amount of DNA matching (siblingship index or sibship index) between the individuals tested.
If the siblingship index is less than 1.0, there is no relationship.
If the siblingship index is greater than 1.0, the tested persons are either full siblings (both parents in common) or half siblings (one common parent).
Based on sibship index values, three results are possible from sibling DNA tests:
- Full Sibling (more than 90% of the genetic match)
- Half-Sibling (50% to 89% of the genetic match)
- Unrelated (relationship not supported)
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Full Sibling vs. Half Sibling Test
Full siblings share both parents in common,i.e., the same biological mother and father.
The genetic information of full siblings is the same for the individuals tested since they share DNA from both parents.
Half siblings share only one parent in common, i.e., either father or mother in common.
The genetic information of half-siblings is different for the individuals tested since they share DNA from only one parent.
Maternal half-siblings share the DNA from only the mother only, and paternal half-siblings share the DNA from only the father.
Full siblings should have a full sibling index value greater than 1 in their sibling DNA test. (full sibship index is higher than half sibship index).
Half siblings should have half sibling index value greater than 1 in their sibling DNA test. (half sibship index is higher than full sibship).
Unrelated individuals should have a half-sibling index value of less than 1.
How Long Does It Take?
Non-legal direct-to-consumer sibling tests can take 8-10 weeks from the time you place an order.
However, some companies deliver the results within a month.
Types of Sibling DNA Tests
A sibling DNA test can be of two types:
- Legal sibling DNA test - For court admissible
- Non-legal sibling DNA test - For personal use
A legal sibling DNA test is a court-admissible test that requires an appointment from the government for all participants.
The samples are collected by a neutral party, like a doctor or lab technician, who is unrelated to the investigating individuals.
Proper witnesses and fingerprints of the involved parties were noted under vigilance.
Legal sibling DNA tests are employed for the following reasons:
- Medical history
- Financial support
- Child custody
- Insurance claims
- Birth certificate changes
- Tax forms
- Other legal reasons
Non-legal sibling DNA test (private DNA sibling test) is for informational or personal use. It is performed at home using a test kit without any assistance from medical technicians.
The reports are the same as the legal tests but are not intended to be used in court.
How Do At-home Sibling DNA Tests Work?
The At-home sibling DNA test kit can be ordered online.
The kit contains all the necessary instructions on how to use it.
The sample is collected by cheek (buccal) swab sticks and sealed in a given envelope.
The buccal cells contain the DNA, which provides genetic information.
The sealed sample is shipped back to the lab, and the results are obtained via mail.
Salivary samples may also be used here.
Can 23andMe Distinguish Sibling Relationships?
If 23andMe genotyped you and your siblings, the relationship is determined based on specific traits.
This feature finds other 23andMe users whose DNA matches yours.
Based on how much DNA is shared, people are categorized into relationships.
The presence of identical DNA sequences in two individuals suggests that they have a recent common ancestor.
The length and quantity of these identical segments determine the relationship between people.
If you have full or partial siblings, your relationship with them is referred to as "siblings" or "half-siblings," respectively.
This feature enables you to compare your genome to that of your siblings.
Full siblings will have more completely identical and some partially identical regions.
Only a small number of regions will be identical in half-siblings.
- A sibling DNA test identifies whether two or more persons are biological siblings.
- The sibship index is the value used to calculate the sibling relationship.
- If the value is greater than 1, they are full siblings, and if the value is slightly less than 1, they are half-siblings.
- The sibling DNA test can be of two types - legal and non-legal.
- A legal sibling DNA test is taken when the court issues an order to submit as proof.
- Non-legal sibling DNA tests are taken at home for informational or personal use.