I admit it; I occasionally have incest dreams. When I told Master this, he said, "Oh yeah, I have those too," which reassures me this is a fairly normal occurrence. Considering how much more bizarre our minds are than we'd like people to believe, I'm not surprised. However, I've noticed there are two distinct types of incest dreams that I have.
The first kind involves actual members of my family, usually my siblings. In these dreams, the sex usually isn't depicted very positively; often I'll perceive a rank, putrid odor while dreaming about it, and even in the dream I often think, "Oh ew, what the hell am I doing?" It almost always involves multiple family members at a time; one time my entire family was there at once. The sex is usually frantic and furtive, and we're usually rolling around in garbage, like rats.
The second kind involves people whom my mind identifies as a family member but who is entirely fictitious. Invariably my "relative" is dashingly good-looking (and often closely resembles Master, ha!) and we always have the classic, angst-tastic, "NO, we cannot do this - our love is forbidden! ...BUT I CANNOT RESIST YOU," scene before making sweet, sweet love to each other. In other words, it's the stereotypical heterosexual (most of the time my "relative" is male) female fantasy, except with a twist.
If I were to hypothesize why I have these two starkly different types of dreams, I'd guess that it's two different ways of my brain playing with the incest taboo, in each case focusing on something different.
Let's face it - taboos are alluring. They're fascinating. They're sexy. That's the whole point of the story of Genesis. We're repulsed by taboos, but it is that very repugnance that makes them irresistible.
So. Incest. Definitely taboo.* But something my brain can't ignore. So it constructs these fantasies to explore this particular taboo. Sometimes it focuses on the reality of incest - that it's having sex with family members. This is something that I'm wired to find disgusting. So when I dream about it, my unconscious expresses its disgust even as it dreams about it. Other times, my brain focuses on why the taboo is alluring, which is because it's "forbidden." Oooooh, fun! Humans, instigators that we are, can't resist forbidden stuff. We love it. So my brain expresses how much it loves playing with the forbidden by constructing the ideal "relative" for me to get nasty with. Tee hee! Aren't I naughty - I'm doing something I'm not supposed to!
I wonder if I have incest dreams at a higher frequency than the average vanilla person, since I'm more in to busting taboos. (FWIW, I have 'em about once a month, if that.)
*Whether it's rightfully taboo is something else altogether, and something I don't know the answer to, so I won't get into that right now.