You're walking down the street with a few friends where you spot someone you know making out with a guy. Only the guy isn't the your friends boyfriend, but her own brother. This isn't just familial pecks on the cheek, it's hardcore making out - kissing on the lips and all. You don't mention it, you're even disgusted by it. And while it may feel unnatural to you, it's anything but unnatural - it's just merely illegal, a rule enforced a long time ago and you don't know the reasons why.

In her 1992 book, Encyclopedia of Unusual Sex Practices, Brenda Love wrote:

The taboo against incest originated for several reasons. Genetic defects in offspring has been cited most often. However, many tribes only restricted marriage between relatives; not sex. The taboos was used to promote kinship with other tribes, and to avoid sexual disruption or confusion of roles in the family unit. Sibling incest was once thought to produce only female offspring. This belief might have been one reason patriarchal societies prohibited these marriages.

But may still cringe at the idea of two people who are closely related doing the nasty - believe you me, I am one of them. Love's book, however, only deals with parent/offspring (I stray away from using the term child because, while many times incest crimes are between someone of underage and his/her parent, many cases have been proven to be with consenting adults; I'm making an attempt to talk about those relationships and not the child sexual assault cases), and does not touch on the subject of siblings. However, she had this to say:

The Egyptian royalty used matrilineal descent in choosing successors because they couldn't prove paternity. Royal sons could only rule if they married their sisters. Sometimes they were married at birth.

That's just wonderful.

What piqued my interest on the subject of brother/sister incest was an article that was e-mailed to me. In it, a woman speaks about her relationship with her brother (the intro to this post was actually inspired by that article) and how natural it seemed, all the while knowing that society would never understand. There are several people out there in the world that have such experiences, hiding them in the closet in order to keep them sacred, secret, safe.

Maybe we'll never understand the incestuous relationship, and maybe we'll never have to, but in the dark they happen more than we think.

I'll touch on this subject again, perhaps leaning to the parent/offspring relationship as well. It'll be heavily researched when it's posted.