Editor's note: this story contains scenes of incest or incest content.
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I have a very unusual relationship with my stepsister Crystal. Our parents were married when we were both twelve, but they had been dating since we were both ten, and we got along swimmingly from the very beginning, so we hardly objected to the merger of our households. However, as we grew older, our close bond took a rather unexpected and ironic turn. By the time we were both 18, we had realized that we were both not only bisexual but also generally hornier than average. While we weren't always actively seeking erotic gratification, we never found ourselves in a mood to turn it down if an appropriate partner was offering it or seeking it for himself/herself. The pleasure was always passively welcomed even when we felt no particular inclination to go looking for it. I suspect that this was partially just a genetic fluke and partially a result of living in a rather sex-positive home. Hell, we had a bit of a hard time understanding why anyone we dated felt awkward making out with us in incidental view of our parents. We just didn't care, and neither did my mom or Crystal's dad.
By the age of 21, both of us had dated relatively little so far, which always perplexed me, because Crystal is just plain hot! After all, she's a doe-eyed redhead with pouty lips, perky 38D breasts, and a firm round butt. Although I'm sure she's the more attractive one, I have a surprisingly similar figure, with the exact same bra size and an ass that looks at least somewhat comparable to hers when I look at it in a mirror. Meanwhile, my eyes are green while hers are blue, and although we both have fairly long hair, my own is practically jet-black in contrast to her ginger tresses. In addition to how sexy at least one of us is, we're also fishing in a significantly larger pool of potential partners than most women (not only straight men, but also lesbians and fellow bisexuals). Our dating life is nevertheless slower than one might expect.
Neither of us could ever complain, though. For one thing, the few relationships we have had tended to be more meaningful. For another, we have no trouble satisfying our sexual needs even when we happen to be single. Obviously, we can both masturbate. In fact, I daresay we've gotten exceptionally good at it, and it's especially easy when privacy isn't as much of an issue as it is for most families. However, it didn't take us long to discover a handy attraction to each other, and for the past few years, we've had no qualms about really putting the "step" in "stepsiblings." In fact, we could probably be best described as "stepsisters with benefits." Whenever at least one of us is feeling that erotic itch, she's free to enlist the other's help in scratching it. Receptiveness is assumed unless otherwise stated, which virtually never happens, at least as long as we're each either single or seeing a guy who's actually turned on by the notion of our arrangement and doesn't mind it. It's all quite pragmatic and frequently downright efficient. Much of the time, foreplay is minimal, and as often as not, we don't even bother to remove any clothing beyond what would obstruct whatever activity we have in mind.
Crystal is particularly alluring to me due to one very particular quirk. She never outgrew sucking her thumb! As she grew up, she managed to train herself to use her non-dominant hand to make it easier to perform other tasks while doing it, but as for the habit itself, she just never felt the urge to stop, nor did any of her parents feel any great need to discourage it, especially since it was so helpful for focus and relaxation. In fact, it seemed so useful that eventually she even got me doing it. I'll never forget the way she'd giggled at me the first time I tried it out of pure curiosity. "No, don't slide it in and out like that. It's not a dick," she'd joked. "And don't suck your cheeks in like that either." It took me a while to recover a skill that was presumably instinctive when I was little, but when I did, I didn't regret it. I had to admit it had an instantly meditative and calming effect. To this day, if either one of us is anxious, nervous, stressed out, or even just bored, the thumb is likely to find its way into the mouth.
We are now both juniors at a prestigious university located within a short drive from our family's house, but that convenience doesn't make college life any easier, even for straight-A students like us. We each have one three-hour block class per week, and those aren't fun even for the nerdiest of us. That is probably why Crystal had her thumb firmly lodged between her lips when I picked her up one afternoon and kept sucking on it all the while I drove us both home. The sexiness of it still hadn't gotten old, and by then, I doubted it ever would. Whenever I could do so safely, I stole glances of her as she indulged in the self-soothing habit. As usual, her left hand was clasped in a loose fist against her nose, with her thumb enclosed as deep as it could go in her mouth. Her cheeks inflated ever so slightly, her rosy lips pulsated subtly against her ivory skin in what nearly resembled a very gentle chewing motion. I idly wondered if I looked that sexy when I engaged in the same behavior.
Anyway, Crystal's thumb didn't even come out when we entered the house and lazily let our backpacks slide off our shoulders. The sight of her still sucking on it so cutely, combined with the way her tank top hugged her breasts, continued to arouse me further, but she seemed unaware as she headed towards the kitchen. I followed her, enjoying the view of her ass, until she reached the refrigerator and opened the door with her free hand.
I approached her from behind, gently pulled her hair aside, pressed my lips to the crook of her neck, and sucked. I heard her gasp and felt her shiver, which only spurred me onwards. I kissed her jawline and then her earlobe, and that did it for her. Withdrawing her thumb from her mouth, she slammed the fridge door, whirled herself around, cupped my face, and captured my lips with hers. I nibbled toothlessly on her lower lip while she did the same to my upper lip. Meanwhile, my arms snaked around her waist and pulled her closer, and I shuddered at the sensation of her ample bosom mashed against mine. My hands drifted lower and gripped her butt, and I managed to smirk proudly through our impassioned liplocks at the squeak it elicited fom her. As she broke away from my mouth just to place a searing kiss at the cusp of my cleavage, I reached breaking point and immediately unfastened her jeans. Purring in anticipation, she reciprocated with equal impatience, and within a few seconds, we were both wearing nothing but panties from the waist down.
Practically growling, I hoisted her up by that lovely ass of hers and landed her clumsily on the nearest countertop. She second-naturedly spread her thighs, and I was instantly standing between them as our lips collided once more. Neither of us could be bothered to take our panties off, as my hips were already rolling instinctively against hers. The pleasure may have been slightly enhanced if we had taken those few extra seconds, but at that point, it felt too good already to be worth it. Our kisses quickly dwindled as it became difficult to concentrate on anything but essentially humping each other's pussies. I grunted as I smacked my vulva against hers a few times before I anchored myself to the countertop and began administering a more steady and desperate friction.
