As Karen was getting her breath back, I told her sister "Donna, if you want, there's a way that I can make you feel good, too, while you help Karen."
I could hear the eagerness in Donna's voice when she responded "How? Never mind… just tell me what I need to do!"
"If you'll move up here so that I can use my mouth on you, then you can lay on top of me; if Karen leans back, then you can use your mouth on her."
I'd barely gotten the words out of my mouth before Donna was moving toward my head; a few seconds more, and she'd gotten herself positioned over my face. Karen sat up, then leaned back to support herself on her arms, which left room for Donna to lay on top of me and get her head between her sister's thighs. Before Karen could start moving on me again, I arched my hips up, filling her with my cock even as Donna was starting to use her tongue on Karen's erect clitoris.
Lifting my head, I was able to slip my tongue between the folds of Donna's labia, where I found that she was practically leaking her essence, she was so aroused. When I started to delicately lap them up, I ran my tongue across Donna's clitoris a few times, and heard her release a deep groan of pleasure.
For the next several minutes, I was in a position that I'd never even thought I'd be in — one of my nieces on my face, while she ate the sister I was slowly fucking. All three of us had not just one, but two sources of pleasure, by virtue of being "connected" to the other two — and it wasn't long before it was clear that each of them found it as enjoyable and arousing as I did.
As Donna continued to use her tongue and mouth on her sister, Karen's excitement increased quickly and dramatically — and the feeling of her vagina as I repeatedly thrust up into her improved, as well. I knew that I wasn't going to be able to hold out when she finally climaxed; the increasing intensity and duration of the fluttering of her pussy as she got closer and closer to that point were simply too much.
Despite the fact that Donna would interrupt her activities with her sister so that she could use her tongue on my penis didn't help — me or Karen, either one. If anything, it only got me going even more, knowing that Donna was getting Karen's taste off of MY cock. It apparently had a similar effect on Donna, as evidenced by the frequency at which she did it; I got the additional benefit of a nearly constant flow of Donna's juices to please my taste buds.
Between the feeling of my man's erection moving in her barely-pubescent vagina, and the attention her older sister was paying to her clitoris, Karen didn't have any problem reaching a climax… a strong one.
I didn't get more than a couple more strokes into her before the dramatically increased tightness of her warm, wet vagina was enough to push ME over the edge, too; with a deep groan, I filled her with my manhood one last time before the first spray of semen erupted out of me -
prompting her to call out "That's it, Uncle Ted! Cum in me!" as she tightened around me even more; a command that I was already complying with, and quite enthusiastically.
When the last drop of cum had dribbled out the end of my cock, I realized that I still had Donna's cute and tasty pussy in front of me… and readily went back to trying to get her off, too, even as Karen's vagina tried to milk my cock for whatever it could get out of me.
Karen didn't wait for my penis to shrink very much before she pulled herself off of it; after she moved to rest on her back and lift her ass off of me, I heard her tell Donna "Clean Uncle Ted off, then you can do me…".
Not more than a couple of seconds later, Donna was using her talented mouth and tongue to clean my manhood of the combination of my semen and Karen's juices — thoroughly, and with considerable enthusiasm. Much sooner than I would have liked, she'd gotten every trace of my cum or her sister's oils; I could feel it when she lifted her head, and Karen edged a bit closer and raised up again so that it was easier for Donna to begin performing a similar service on her.
With nothing else to concern myself with, I began to apply myself to making sure that Donna wasn't any less satisfied than Karen or I had been. I still wasn't about to tease her into anything too severe, but that didn't mean that I couldn't make it damn good for her. I knew that I was having the desired effect when Donna began having to stop vacuuming her sister's pussy so that she could release increasingly louder and more passionate moans as she began to press her pelvis down onto my mouth and tongue.
Karen finally pulled herself away from Donna's face, and lay down between my legs, with her legs draped over mine. With nothing to distract her from what I was doing between her legs, it wasn't but another minute or so until I was able to give Donna the kind of pleasure she'd brought me and her sister. While I refrained from making it as intense as it could have been, I didn't skimp on trying to make it last as long as I could, by alternating between gently massaging her clitoris and trying to see if I could get my tongue through the then-minuscule opening to her vagina. When her release was over, Donna managed a barely-controlled collapse that ended with her laying on top of me as she panted for breath.
It wasn't long after that that I heard Karen's voice say "No, you don't have to go. Come on in, if you want."
I couldn't figure who she was talking to until I saw an awed Wendy hesitantly come in and take a seat on Donna's chair, where she just sat, practically staring at all of us.
My first thought was "Oh, crap…"; shortly followed by remembering that there wasn't anything that I needed to worry about, or be afraid of. Still, I had considerable interest in finding out what Wendy thought of what we'd done (or, at least, however much of it she'd seen).
Karen was the first to move by sitting up and getting her legs back underneath herself. Seeing that Donna was laying on me, Karen moved to sit by my hip and asked me "Would you like some help getting her off of you, Uncle Ted?"
"Thanks, Karen, I would.", I answered.
Donna was able to provide a little more than token assistance in helping Karen and me get her sitting up next to me; then when I'd moved to sit up and lean against the headboard, we got Donna next to me where I could help hold her up. That done, Karen didn't hesitate to sit astraddle my lap and lean back against my chest, where she pulled my other arm around her waist. All three of us simply looked back at Wendy for a few moments before Karen told Donna and me "I thought I heard a noise, and when I looked, Wendy was standing in the doorway looking at us.
She started to leave, but I told her it was okay to come in." Following that, Karen asked her younger sister "How long were you there, Wen?"
I could see Wendy blushing slightly as she answered "Uh… since before you had an orgasm. You know, when Uncle Ted's penis was in you."
"So you saw pretty much everything?", Donna asked.
Wendy nodded, blushed again, and answered "Um, yeah… even that you… you were using your mouth on Karen, and that Uncle Ted was doing it to you."
"What do you think about that?", I had to ask. "Did you think it was scary, or silly, or what?"
Wide-eyed, Wendy answered "At first I thought it looked kinda scary. But then I remembered that I came to see what was going on because of the funny noises, and decided that it sounded more like you were, um, feeling good than being hurt, and I stopped being scared. I… I never thought about anyone using their mouth like Donna and Uncle Ted were doing, but when I started thinking that it… it looked like it probably felt REAL good. I didn't know that Uncle Ted and Karen were having sex, and I was really surprised to see that he could even fit in her, but it sure looked like she liked it. I've been touching myself, you know, and even had orgasms — but I don't think they've been anything like what it looked like what happened with Karen and Donna!"