"What should we try next?" Karen asked playfully. The question echoed playfully within my head unleashing a slew of deviant desires that I'd never before dreamt possible. Unfortunately before my racing mind could settle upon a properly perverse plan for what to do next I felt the car begin to slow as Dad pulled off the highway.
Karen silently slipped her tongue into my mouth for one more kiss before climbing over the seat into the pile of pillows and blankets in search of her formerly forsaken top. Shifting my gaze out the window I realized we were pulling into a highway rest area. Just as Dad eased into park, Karen maneuvered her now fully clothed body back over the seat and settled herself next to me.
Unable to follow as Karen and my parents exited the car I remained stuck, contentedly, under Sarah's slender legs as she slumbered on. It still amazed me that she hadn't woken after all Karen and I had done to her enticingly lithe young body. My Curiosity about the matter was short lived though as Mom poked her head in the open door to say "Oh, Hun you can go ahead and climb out for a stretch. Sarah took a very strong sleeping pill before we left, and won't be up for hours". "Sarah takes sleeping pills...why didn't she say anything?" I asked, trying not to let my excitement show.
"Well she is a little embarrassed that she needs them. You know how she can be. Don't tell her I told you, Ok? I just didn't want you to be stuck in there."
"Sure thing Mom I won't say anything to her" I replied as I slid myself out from under my sister's legs.
Stepping out of the car I lifted my arms overhead to stretch out my muscles. Unable to stifle a yawn after my long stretch I set out in search of the restroom with my mind tangling into knots contemplating all that had happened and all that still could. We spent ten minutes or so at the rest stop before Dad let everyone know it was time to pile back into the SUV. Heading towards the exciting possibilities of the car I found myself walking behind Mom and Karen whose conversation I couldn't help but overhear.
"Karen sweetie would you mind riding up front and navigating for your father so that I can nap for a bit?" Mom asked using her sweetest Mom voice. Doing her best to contain her disappointment at being denied more back seat merriment Karen reluctantly agreed to the seat swap. Fairly disappointed myself I sped up to pass them and climbed in ahead of my cock blocking mother, and slid myself back under Sarah's waiting legs. Mom hopped in after me smiling at how cure she found Sarah sprawled out over my lap. If she only knew that right then her sleeping daughter's exposed belly was full of my cum. Cum delivered by her other daughter's talented mouth. My face split into a huge grin at the filthiness of it all.
Five minutes down the highway my hopes were rekindled when Mom decided she'd sleep better lying down and quickly disappeared into a cocoon of blankets behind the seat. Finding myself in a semi-private situation with my little sister, who seemingly would sleep through anything, I began to form a plan. Eager as I was a few minutes of patience to allow Mom to drift off ensured no intrusions for the foreseeable future. Mom's soft snoring was all the incentive I needed to set my plan in motion. Slowly, I reached over to once again raise Sarah's top over her bare breasts. Her perfect tits begged my touch and teased my imagination. Restraining my urges, for now, I grasped each side of her tight yellow shorts and gently slid them down to her knees. My eyes feasted on a well trimmed tuft of blonde hair and a deliciously tight little snatch. My cock was throbbing and my pants were again being soaked with precum. Wasting no time I slipped out of my pants freeing my cock. Luckily Sarah's pillow against her window blocked any easy view from passing cars. Sliding further over with my cock poking up between her legs I squeezed my aching hard on in between her thighs and right up against her exposed pussy. It was tricky with her shorts around her knees, but finally the base of my cock was slightly parting her pussy lips as the head stood eagerly oozing precum high over her cute blonde pubes. Everything was ready for the next part of my plan. I grabbed my phone held it to the side of my cock angled towards Sarah's face and snapped a pic.
Checking out my own handiwork I had to admit the picture came out perfect since it was taken from near her feet and at just enough of an angle that everything from her tits to her pubes brushing my cock was clearly visible. Smirking at my own deviousness I opened a new text to Karen, wrote 'Miss ya back here', attached the pic, and hit send. It didn't take long for Karen to reply. Her text read 'OMG! That is so fucking Hott! If she wakes up she will freak!'
Knowing that her heavy duty sleeping pill meant she wouldn't be likely to wake I decided to push things further. Reaching back careful not to wake Mom I grabbed another pillow to block the other side window then got to work. First her shorts then her top slipped effortlessly off leaving my little sister, who apparently didn't believe in underwear lying completely naked with my hard cock between her slender toned legs. Lifting her hand from between her side and the seat I positioned her fingers around my cock, and was about to take another picture when a better idea surfaced. Switching my phone to video and hitting record I started to lower and raise my hips. If her sleeping face hadn't been in the frame it would have looked like she was jacking me off with her thighs and hand. After ten seconds I ended the recording, attached it to a text, and wrote 'what's the matter...scared? Didn't seem to worried when spit a load of my cum down her sleeping throat sis ;) '
Waiting for Karen's reply it was obvious that even deep in a pill induced slumber Sarah's body was responding to my attention. The side of my ten inch cock was coated with her warm juices and even with my movements halted her sweet nectar continued to flow against my manhood and down onto my lap and balls. Reveling in Sarah's unwitting arousal I almost jumped when my phone buzzed its announcement of Karen's response.
K 'You are so bad! I am so wet for you...put it between her tits for me : ) '
Having anticipated Karen making a request my response was already ready.