Similarly to a paternity test, even if the possible or alleged father is dead, one can check whether two or more siblings had the same father. Should the parents not be available for a test, siblings of the parents or the grandparents can be tested in order to answer descendancy questions.
In principle it is possible to make a statement solely from their genetic profiles as to whether two or more people are siblings or relations or not. These tests are either called indirect paternity tests (as they test paternity without a sample of the father) or simply sibling or kinship tests. The provision is the analysis of DNA samples of the persons involved. If, in addition, samples from the biological father or the mother are available for analysis the sibling or relationship test can achieve better results. Depending on the combination and comprehensiveness of the test, values of greater than 99.9% can be reached. However, in general, probability values for siblings tested without the father or mother are lower compared to a standard paternity test with samples of the father and mother.
Possible kinship or sibling testing cases
- brother - brother
(e.g. by testing the Y-chromome which is only found in the paternal line of heritage)
- brother - sister
(to achieve best results a sample of the mother should be included in the analysis)
- sister - sister
(best results are achieved with a sample of the mother)
- grandfather - grandson
(by testing the Y-chromosome or with a sample of mother or grandmother)
- grandmother - grandson or granddaughter
(best with mother or grandmother)
- aunt or uncle - niece or nephew
(again a sample of the mother would increase the probability)
- grandfather/grandmother - grandson/granddaughter
(the test between cousins requires additional reference persons' samples)
Tailor-made kinship testing
As the informational value of sibling tests varies depending on the family constellation and available samples in each individual case, bj-diagnostik offers personalized and customer-individual consultation for indirect paternity testing and complex kinship analyses: Every customer receives a tailor-made quotation considering the exact strategy of analysis proposed to solve the genetic kinship relation in question. This also includes an estimation of the achievable probability of relatedness based on the information and samples available. In addition, bj-diagnostik is able to consult the customer on how to improve possible test results. Many laboratories offer just “one size fits all” packages for any kind of sibling or kinship analysis, so that customers overpay to solve simple analysis problems or cannot achieve solutions for their more complex cases.
If the people in question are male, we can research paternal lines of origin with help of the Y-chromosome marker and achieve very precise results regarding the degree of relationship.
Immigration indirect paternity testing
Indirect paternity testing is often needed for the purpose of immigration and is readily available in our laboratory. German authorities may require a DNA test to prove a given relationship to enable immigration, for example in the context of a family reunion. Recently bj-diagnostik could prove that two refugee children from Lybia are related to the sister of the mother who is married to a German citizen and legally living in Germany. Consequently, immigration to Germany had been easy for her nephews as two proven full siblings.
The sampling for immigration testing often has to be organized via local German embassies. bj-diagnostik team members help to organise the sampling process.
For the research, we need mouth swab samples or other test material.