DNA testing can help in cases where there has been suspected incest. There are different types of incest, but across most cultures it is considered taboo and is moreover, illegal. Incest between brothers and sisters is the most frequent followed by incest between father and daughter. Even if there is consent between the people in the incestuous relationship, it is generally still considered illegal.
The Sibling who is Actually a Parent
In some cases one sibling might actually be the parent of the other sibling. This may not necessarily be the result of an incestuous relationship though it may at times be so. Let’s take an example. Jill and Sandra are sisters; however, what may have happened is that Jill got pregnant in her early teens with Sandra. Sandra was taken into care by Jill’s grandma and the grandma raised Jill and Sandra as siblings. In this case, it would not be possible to do an MtDNA Test (mitochondrial DNA test) because Jill and Sandra will share the same MtDNA; this is independently of whether they are siblings or whether Jill is actually Sandra’s mother. A full maternity test would conclusively determine whether Jill is Sandra’s mother or not.
Sister- Brother Incest and DNA Testing
Mark and Susan had an affair- they are full siblings. Susan got pregnant and had a child- Jane. The child, Jane, grows up to suspect that Mark, her uncle, might in reality be her biological father. What can she do?
Ideally, she could do a paternity DNA test. This would involve getting a DNA sample from Mark and seeing whether their DNA profiles are the same- if they are, it would confirm that Mark is not her uncle but her father.
The next option, should Mark be dead or unavailable, is to carry out a DNA paternity test with one of Mark’s children. Mark’s children can either be Jane’s cousins (if Jane is not Mark’s daughter); or, alternatively, if Jane is Mark’s daughter, the children would not be her first cousins but her half-siblings (they would have a common father).
Sibling DNA testing very much depends on the gender of the people involved; there can be different options available depending on whether the people are male or female. However, whichever way we look at it -whether Jane and Mark’s children are just first cousins or half siblings-there will still be considerable amounts of common genetic material.
DNA testing can help solve cases of suspected incest- however; depending on the specific case the test might not be conclusive.