Genetic sexual attraction

Genetic sexual attraction is a concept in which a strong sexual attraction may develop between close blood relatives who first meet as adults. There is no evidence for genetic sexual attraction being an actual phenomenon, and the hypothesis is regarded as pseudoscience.
Background.
The term was coined in the US in the late 1980s by Barbara Gonyo, the founder of Truth Seekers in Adoption, a Chicago-based support group for adoptees and their new-found relatives. She developed sexual feelings for her son when she met him after he was adopted away, but he did not want to be part of any such contact.
Because many traits are at least partially determined by genetics, genetic sexual attraction is presumed, according to those who believe in the concept, to occur as a consequence of genetic relatives meeting as adults, typically as a consequence of adoption. However, this is a very rare consequence of adoptive reunions.
Another suggested explanation for the phenomenon is possible narcissistic feelings.
Incest is extremely rare between people raised together in early childhood due to a reverse sexual imprinting known as the Westermarck effect, which desensitizes them to later close sexual attraction. It is hypothesized that this effect evolved to prevent inbreeding.
Direct studies.
Although reported frequently as anecdote in the field of psychology, there are no studies showing that people are sexually attracted to those genetically similar to them. Studies of MHC genes show that unrelated people are less attracted to those genetically similar to them. However, in mice, this lack of attraction can be reversed by adoption. While it has been documented that sexual attraction can occur between related individuals in some cases, it is not clear that calling this attraction GSA is appropriate.
Criticism.
Critics of the hypothesis have called it pseudoscience. Amanda Marcotte of "Salon" has stated that the term is nothing but an attempt at sounding scientific while trying to minimize the taboo of incest. She also expressed that many news outlets have handled reports of the subject poorly by repeating what the defenders of the hypothesis have said as opposed to actually looking into the research on the supposed phenomenon. She states that most of the publications which have chosen to run stories of couples speaking about "genetic sexual attraction" are not legitimate news sources and that one of the blogs which were written by a woman in an incestuous relationship simply reads like a story of a young girl who has been groomed by her father. The use of "GSA" as an initialism has also been criticized, since it gives the notion that the phenomenon is an actual diagnosable "condition". Eric Anderson, sociologist and sexologist, states that the one single academic research paper on the subject uses "Freudian psycho-babble".
Catherine MacAskill, an adoption and child sexual abuse expert, stated that "although [...] concerns are understandable [for adoptees and biological parents]" before attempting a reunion, one who researches the subject will realize that so called "genetic sexual attraction" cases seem to be associated with sudden unplanned meetings which lack the proper safeguards of a thoroughly prepared reunion.