Michigan mom Aimee Louise Sword has been sentenced to at least nine years in prison for having sex with the 14-year-old biological son she gave up for adoption when he was a baby. In the Detroit Free Press article about Sword's sentencing, prosecutor Jessica Cooper says, "It’s the first time I’ve really seen something like that between a mother-son. But I have seen it unfortunately many times between a father-daughter." Though the notion of a parent having sex with his or her child is repellant to most, it is not unheard of in cases like Sword's, where the child was not raised by the parent in question.
It's called Genetic Sexual Attraction, and a Guardian article from 2003 says that the phenomenon is "increasingly acknowledged by post-adoption agencies to be a common feature of reunions between blood relatives who have never before met." The Guardian is using somewhat vague language because it's not something that has been studied very much: A CBC article from last year says there is only one piece of academic research on GSA. A British doctor and former adviser to London's post adoption center named Maurice Greenberg looked at 40 reunions of blood relatives who were meeting as strangers. According to the CBC:
[Greenberg] says interviewees described emotionally charged meetings and the shock of familiarity as they noticed the same interests, traits and mannerisms in their relative. Many described it as feeling like they were looking into a mirror. Combined with the feelings of loss and trauma associated with being put up for adoption and the excitement and fantasies of a reunion, the adoptees often felt vulnerable to such attraction.
GSA was in the news last year because of Mackenzie Phillips revelation that she had had "consensual" sex with her father, Mamas and Papas singer John Phillips. Sword connected with her son via Facebook, and it's possible that reunions among long-lost blood relatives will become more common with the rise of social networking. Since the vulnerability Greenberg described sounded accurate, this is probably not the last we'll hear of unfortunate cases like Sword's.