Incest refers to any illegal/socially unacceptable sexual activity between close relatives, usually within one's immediate family. Common incestuous cases involve adult men and their daughters, and sometimes also siblings have incestuous relations. In these types of incest cases, it is possible that a child may result, and it may be difficult to conclusively identify the child's biological father. When a DNA test is performed between a close male relative of the biological father, i.e. brother or father, of a child, and the child, the non-father could possibly be falsely identified as the biological father. Or, for example, in the case of a child produced from brother-sister incest, it is very likely that the alleles inherited from the mother are included in the father‘s DNA profile. However, today's DNA tests can definitively determine paternity, even in incestuous cases.