What is genetic cuckoldry?

Genetic cuckoldry refers to a situation where a man believes he is the genetic father of a child, but it turns out he is not. This could be due to the mother of the child having a relationship with another man, such as a neighbor or someone she is having an affair with. The term is derived from the behavior of the cuckoo bird, which lays its eggs in the nests of other birds, deceiving them into raising its offspring 1.