Identifying fathers with identical twin brothers is difficult with prenatal paternity DNA testing.

Summary of this article

Is it possible to use DNA analysis to determine if a sibling with identical twins is the father? This section details the genetic similarities and limitations of the test.

If identical twin brothers are potential fathers, it is very difficult or impossible to determine the father in a prenatal paternity test. This is due to the following reasons

DNA characteristics of identical twins.

Identical DNA: identical twins arise from the division of identical fertilized eggs and therefore have almost identical DNA sequences. Therefore, STR markers and other genetic analysis methods used in standard DNA identification cannot distinguish between two people.

Issues in prenatal paternity testing.

Identity: if there are identical twin prospective fathers, the fetal DNA obtained from the prenatal paternity test cannot distinguish which twin it was inherited from .As both twins are equally likely to be the father, the results of the test will not help to identify the father.

Possible solutions.

Additional evidence or information: in order to identify the father, additional evidence or information other than DNA evidence (e.g. duration of the relationship or other circumstantial evidence ) may be required. However, this too may not be scientific evidence, but only a legal determination.
Epigenetic markers and mutations: recent studies have attempted to differentiate twins using epigenetic differences and a small number of novel mutations that occur between identical twins, but these methods are very limited and are not yet widely used for general appraisal.

Summary

When identical twins are potential fathers, it is very difficult to identify which one is the father in a prenatal paternity test and cannot be distinguished by normal DNA testing. At present, it is understood that it is difficult to identify the father, as it is only possible to rely on non-DNA evidence and very sophisticated genetic analysis methods.