What was once a taboo has now become, to many brothers and sisters, a cool pastime and an even cooler way to make money online. Brother-sister incest seems to be on the rise, at least according to my unofficial survey of incest websites. In perusing websites that feature incest, I found two types of brother-sister incest clips. Both were more prevalent than in previous years.
Can sex between brothers and sisters ever be normal?
Incest - Wikipedia
In an interview published Monday, Hollywood director Nick Cassavetes, whose new movie Yellow tells the story of a fictional love affair between an adult sister and brother, claimed that incest is just the latest frontier in people throwing off the shackles of rigid, cultural convention and following their hearts. We had heard a few stories where brothers and sisters were completely, absolutely in love with one another. You know what? This whole movie is about judgment, and lack of it, and doing what you want. Who gives a shit if people judge you? Love who you want. Gay marriage — love who you want?
Sex among siblings: a survey on prevalence, variety, and effects
Siblings play a unique role in one another's lives that simulates the companionship of parents as well as the influence and assistance of friends. However, though a sibling relationship can have both hierarchical and reciprocal elements,  this relationship tends to be more egalitarian and symmetrical than with family members of other generations. Furthermore, sibling relationships often reflect the overall condition of cohesiveness within a family. Incest between siblings is most often short-term innocent sexual experimentation by children, but has been an intentional practice among some historical ruling families. The content and context of sibling relationships varies between cultures.
The incest taboo is one of the most widespread of all cultural taboos , both in present and in past societies. In most cases, the parents did not have the option to marry to remove that status, as incestuous marriages were, and are, normally also prohibited. A common justification for prohibiting incest is avoiding inbreeding : a collection of genetic disorders suffered by the children of parents with a close genetic relationship. In some societies, such as those of Ancient Egypt , brother—sister, father—daughter, mother—son, cousin—cousin, aunt—nephew, uncle—niece, and other combinations of relations within a royal family were married as a means of perpetuating the royal lineage. However, sexual relations with a first-degree relative meaning a parent or sibling are almost universally forbidden.