Kuckuckskind

Kuckuckskind (plural - kuckuckskinder ) is a German term used to describe a child whose biological father is not the same as the man who raises the child, and both the child and the social father believe they are biologically related. The term was inspired from the cuckoo bird's nesting habits, which involve laying eggs in other birds' nests—a phenomenon known as brood parasitism.

In case of kuckuckskind, there is no legal relationship between the child and its apparent (social) father. In the context of a marriage, the child is considered the stepchild of the husband, as there is no biological connection between them. When the mother is not married to the biological father and conceals this fact from the apparent father, it legally constitutes falsification of civil status.

The term Kuckuckskind (cuckoo child) is often used colloquially in a derogatory manner in German-speaking countries. It reflects societal criticism directed at the mother for "fostering" a child conceived with another man upon her (marital) partner.

Statistics
According to a British study of family relationships conducted between 1950 and 2004, the median rate of so-called “paternity discrepancies” was 3.7 percent.