Incest which has always enthralled, confounded and horrified human beings occurs as a major and common theme in Western literary tradition. In Hong Kong literature, it is usually deeply disguised and rarely treated in explicit terms. This paper first renames incest and then redefines it. The major theories about the origin and use of the incest taboo and prohibition are summarized and discussed and then tested against Hong Kong literary works with incest themes. Efforts will then be made to analyze, with reference to Hong Kong literary works, whether or not the social advantages of the incest taboo and prohibition are enough to outweigh the disadvantages. The paper concludes with the claim that universal fraternity should be reasserted.