Incest, gamete donation by siblings and the importance of the genetic link.

Recently, several requests have emerged in which women wished to be impregnated with donor eggs fertilized with spermatozoa of their brother. An important argument advanced against such applications is that it is a kind of incest. Four definitions of incest are reviewed in this article to evaluate the acceptability of these demands. The first three (sexual intercourse, reproduction with gametes of first-degree relatives and symbolic incest) do not apply to the cases. However, when the sister and her brother intend to raise the child as social mother and father, these requests should be considered as "intentional incest". If the brother only functions as an uncle, the request of the woman resembles the currently accepted practice of oocyte donation from sister to sister. In that case, the wish to receive gametes from a first-degree relative is motivated by the wish to establish as far as possible a genetic link with the child.