http://www.avclub.com/article/sibling-i ... way-221229
说起来真的是很多古代神话都有这个桥段，深刻地种植在各族人民的集体无意识中，甚至特有道德禁忌特多的中国神话里都有伏羲女娲（？）兄妹乱伦的创世神话。
忽然想起来，神话大杂烩的星球大战（第一集）也曾经 toy with brother/sister incest，记得 George Lucas 在哪里承认过是从伊朗神话里偷来的，当然他只是暗示了一下没敢真下手。
文章里引用了一大堆采用这个 trope 的电视作品。我记得看过 Sam Shepherd 的某个话剧里也用到，以及 John Sayles 的电影 Lone Star。这种 half-sibling 的桥段在现代文艺里算是仍可接受。正如文章所说，身不由己地爱上了自己（失散多年）的亲姐妹/兄弟，是一个载体和符号，即使我们自己对亲兄弟/姐妹毫无越轨的感情，但是对于本能和社会禁忌的冲突却是普遍的，可以说绝大多数人都能产生共鸣。现在同性之间爱情不能作为禁忌的载体了 --- 虽然可以设定在禁止同性恋的时代，但在现代读者的脑子里却失去了大半效果 --- 估计 sibling incest 的故事只会多不会少。
关于禁忌对于人的魅力，精神分析学早就挖掘过了。不过我还没研究过。
Penny Dreadful has spent its second season gleefully dismantling audience expectations amid high-gothic imagery and subtext. One of its major arcs this season is a deconstruction of the Bride Of Frankenstein, as the good Doctor kills and resurrects prostitute Brona to sate the demands of his first creation, Caliban. But in the season’s eighth episode, Brona (now renamed Lily) turns the tables on Caliban—a student of poetry and mythology with some distasteful ideas about what Lily owes him—by propositioning him first. The deal: She’ll be his lover if they kill their maker together. And the term of endearment that seals the deal for mythology-buff Caliban? She wraps her arms around him and calls him, “My brother."
Consensual sibling incest as a fulcrum for narrative is nothing new; it’s been a powerful storytelling dynamic since people started telling stories. It’s a taboo that suggests some inherent separation from the accepted, but avoids the power imbalance (and even deeper taboo) of incest between generations, which is almost always depicted in myth as a curse rather than as merely outré. Brother-sister relationships appear in Egyptian, Norse, and Greek legends, often between heroic deities, and in many of those tales the offspring from those pairings are destined for something equally mythic. Later stories walk an uneasy line between mythic incest and real-life taboo; Arthurian myths heavily feature Morgana and Arthur’s tragic and unwitting union, and emphasizes the bittersweet destiny of their son Mordred, who eventually slays his father.
And despite providing endless fodder for parody—Supernatural has broken the fourth wall repeatedly to make fun of incest ’shippers, and The Spoils Of Babylon riffed on sweepingly earnest star-crossed sibling lovers for hours—it’s a taboo that still entices. Its inherent sense of danger and implication of overwhelming passion makes it an evergreen source of forbidden interest. It’s a family battle without the violence, a Greek tragedy without the need for gods, and an insta-obstacle for its lovers to struggle against. But there’s just enough pathos beneath the suspense that even when the context isn’t mythic, the sense of inevitability still is. It’s a nearly foolproof narrative combination that’s thousands of years old, and has only become more popular as serial storytelling takes full advantage of the narrative tension it provides. Victorian potboilers couldn’t get enough of the “I feel a strong pull to this amnesiac about the same age as my long-lost sister” trope, and neither can we.
In modern television, parent/child incest is still the skin-crawling territory of Law And Order: SVU or Bates Motel, both of which paint it clearly as abuse. But with the one-two punch of dramatic potential and mythical forebears, sibling incest is more common.
Either way the story’s spun, the use of sibling incest usually suggests that something is somehow both very wrong and very interesting. Game Of Thrones has its share of such couplings amid its sprawling cast: Daenerys Targaryen comes from a family line famous for its Egyptian-style royal incest (and her brother seems as though he’d be similarly inclined if his lust for power wasn’t getting in the way of his other lusts). But for all the tragedy that follows that family tree, that incest is part and parcel of greater myths, since the Targaryens are also the most otherworldly of the ruling families: the dragon riders. The series’ more present-tense incestuous couple is Jaime and Cersei Lannister (twins—another powerful relation in many mythologies), who are a less rarefied depiction of the trope. Their passion is powerful but illicit, and neither one of them is a particularly good person: Throughout the first season, their only redeeming value is their love for one another and their connection after they’re parted and overcome by events. And things get even more emotionally complicated for them in the series than in the books, as an intimate reunion scene portrayed as consensual in the books was filmed as rape on the show. It takes that aspect of their relationship from a consensual one to something more abusive—which dismantles the delicate balance of a trope that requires everyone to be willing in order for sibling incest to be a story about a relationship rather than a crime.
Of course, that’s the trick about incestuous siblings, no matter where they fall. While incest can always be used as a neat shortcut to signal darkness or conflict, the mythic element of it actually rests on the subtext of the inexorable fate of those thwarted souls, which is almost always framed as outside the control of the siblings in question. On television, incest defines and directs the people in it in a way that occurs in very few other relationships; the happiness or sadness of a relationship of sibling incest is preordained by the narrative, and the characters powerless to fight against it. (They have to be, for this to work; no one chooses to break the taboo unless circumstances are somehow beyond their control.)
