I fully expected it when Sis wanted to know if it would be okay if Charlene spent Friday night. It being for just the one night, instead of both, Mom and Dad said they were okay with it if Charlenes folks were. A couple of days later, Charlenes mom called to let them know they were fine with Charlene staying over for one night while it was just us "kids" in the house.
From the time Dad let us know about the conference until they left, neither Eva nor I went out of our way to do or say anything to "prove" we'd be okay; we'd talked it over, and decided that doing anything else would just make them worry that we were up to something. Sis and I both fully expected that a lot of the time that Charlene was there would be spent with the three of us together and naked, but as far as we were concerned, that didn't count as "up to" anything — at least, nothing like a coed naked TwisterA® tournament, anyway.
Mom and Dad apparently left the house shortly after lunch, since Mom left us a note that Sis found when she got home from school. Supper that night was re-heated leftovers from the fridge (Mom thoughtfully provided instructions that we didn't need), followed by the two of us watching a little TV
between bouts of making out with each other (and losing various bits of inconvenient clothing along the way). The only real surprise was when Sis invited me to spend the night in her bed; I didn't hesitate to agree wholeheartedly. Both of us readily got naked, and we readily spooned with me behind Eva, my arm around her and cupping her breast in my hand. With my cock nested between Sis' ass cheeks, I couldn't help but get an erection, but all she did was turn her head and in mock sternness tell me "Behave yourself, Billy!"
I assured her I would, and gave her a little kiss on her earlobe before she turned her head away from me again. A little while later, both of us were fast asleep.
The next morning, it was a delight waking up with her tucked into my side with an arm and leg draped across me. I could feel her breasts pressed into my side and her bush against my hip, and was content to just lay there and enjoy the feel of her body next to mine until she woke up a few minutes later. After a few moments, she looked up at me with a pleased smile on her face before telling me "I could get used to waking up like this real easy."
I just smiled back and gave her forehead a quick kiss, then answered "I could too. Good morning, Sunshine."
She rested her head on my pec for a couple of minutes before saying "As much as I'd like to stay here like this all day, I think we'd be in trouble if we didn't show up for school", followed by throwing the covers back and getting out of bed. Unashamedly standing there naked, she turned and told me "IF you can get your lazy butt out of my bed, I'll let you take a shower with me; then you can make us some breakfast while I make my bed."
That was all the motivation I needed to clamber out of bed, too. We put an arm around each other and made our way to the bathroom we shared, where we had a much easier and nicer time waking up than we usually did. After breakfast, it was off to school for both of us, though we took different routes: Eva went one direction to meet up with Charlene while I went another direction so I could walk with a couple of friends from school. The rest of the day was about as normal and routine as it could be.
As agreed, Charlene didn't come over until shortly before supper… that so all of us could have plenty of time to get our homework out of the way, so nothing would get in the way of our time together.
Supper was light, and quick; once we were sure nobody would be stopping by, we made a mass migration to Evas room. It couldn't have been more than sixty seconds before all of us were naked and molesting each other on Sis' bed.
A little while later, they'd gotten me stretched out on my back while the two of them were industriously engaged in getting my cock as hard as they could. I was laying there with my eyes closed when I felt them change positions; to my surprise, I felt someone move to straddle my hips. Figuring that Charlene had been talked into actually showing Eva what sex was all about, I didn't concern myself about it too much. It actually felt pretty erotic when a soft hand gently took hold of my saliva-slick erection and levered it up so the wet entrance to a pussy could capture the end of it. The hand continued to hold me in place as my manhood began to be enveloped by a warm, tight vagina. There was something of a struggle at first, since my cock didn't seem to want to slide into the wet chamber being offered to it; but after a few seconds and a little more pressure, I felt it as I suddenly slid into the hot, tight sheath.
Knowing how small Charlenes vagina was, and it having been a couple of weeks since we'd last made love, I didn't think anything about it. Instead, I was treasuring the feel of hot, wet, and delightfully tight pussy slowly encasing my erect penis. Just as had happened with Charlene the first time, I'd get a little farther inside, then there'd be a pause before there was a bit of backtracking to make sure the two of us stayed lubricated, then some more progress.
I wasn't really paying any attention to how long it was taking, since I was content that it was happening at all. Anyway, it was soon enough that I felt a nice, smooth ass settle onto the tops of my thighs while my cock was thoroughly encased in womanhood.
I'd never rushed Charlene, and was fine with just laying there and enjoying the sensation of having my erection buried in womanflesh while said womanflesh was going through an assortment of tightening and clenching as she made small movements on top of me.
As I waited for the one straddling my hips to start moving, I felt the other person shift toward my head, and thought "Oho! We're going to do something different now!"
A few moments later, and the end of a nipple was softly dragged across my lips; I opened my mouth in invitation, and was rewarded with the end of a mammary being offered to me. I got my lips fastened around it, and no more than ran my tongue across the nipple before knowing who it belonged to: the nipple I'd just licked was hard and long enough that it could only belong to Charlene. Which meant that it had been Eva that had straddled my hips and then proceeded to impale her virgin pussy on my stiff member. I'd just taken my own sisters cherry!
While releasing my liplock on the breast I'd been offered, I opened my eyes and immediately saw that I was right — it was Charlene at my head. After managing to get myself propped up on my elbows, I looked down to see that Eva was looking at me with trepidation. Before I could say anything, though, she spoke first: "I'm sorry to have to surprise you like this, Billy, but I thought it was the only way that I'd ever be able to make love with you."
The expression on her face and what she'd said were enough to keep me from saying any of the things I'd meant to in favor of asking "What do you mean?"
"I mean just what I said. When I asked you if you thought it would be okay for a brother and sister to make love, you didn't tell me 'no' — but you didn't exactly tell me 'yes', either. Sure, you gave me a bunch of reasons why it might not be a good idea, but you never gave me any sign that you'd be okay with it if that stuff was taken care of, either. And you sure didn't act like it was anything we could or should talk about, either; you just said a bunch of stuff and then shut up."
I thought back to the conversation we'd had, and as I replayed it in my mind, I had to admit that she wasn't exaggerating. Regretting what I hadn't done or said (for a change), I looked into her eyes and contritely responded with "I'm sorry, Sis. I really didn't mean for it to come across like that. All I wanted to do was make sure you knew that it was important enough that we had to really think about it first, and be sure."