Marilyn stroking my cock was the best thing I ever felt. I couldn't wait for the next time we had the house to ourselves.
Well, I didn't have to wait very long. Two days later our parents announced that they were going to a business meeting Dad had on the west coast and that Marilyn and I would be staying home. Oh darn...
I had just gotten my driver's license so it was my job to take Mom and Dad to the airport.
"Take care of your sister," Dad said, " and no parties!"
A little voice in my head said, "No problem!"
When I got home Marilyn was out laying in a chaise by the pool. She was wearing a thong bikini that covered her private parts, but just barely. The top was two little patches of cloth that hid only her nipples. The bottom was even smaller.
"Where did you get that," I asked? I couldn't take my eyes off of her.
She pulled her sunglasses down just far enough to look over the top of them. "I bought it a few weeks ago. Been hiding it from Mom and Dad. Do you like it?"
Before I could answer she looked at my crotch and smiled. "I think you do."
There was no denying that I liked it. My dick was already solid.
"So, what have you got planned for today?" I said matter of factly.
Marilyn shrugged. "I don't know. I thought about going to the mall with Becky or maybe a movie with Sally."
My heart sank. I was really hoping for another handjob.
She pushed her glasses back up and layed her head back on the chaise.
"Or maybe I'll just stay here and watch you jack your cock."
"That sounds like fun," I said then added, "It would be even better if I could see your tits while I did it."
"Hmmm, you think so," she said through a smile.
My cock twitched in my pants.
"Well, take it out and let's see what happens," she said.
"Out here, by the pool?"
Marilyn looked around. "Why not? It's just you and me out here." With that she reached behind and untied the bikini top letting it fall away.
Her tits were everything I had imagined and more. They were perfectly symmetrical and her nipples were just as perfect pointing straight ahead. From the looks of it I thought she was enjoying this a little more than she was letting on.
"Okay, start jerking it."
I took my cock in my hand and began stroking while I stared at Marilyn's perfect breasts. She, in turn, stared at my cock which was already oozing a clear sticky liquid.
"Come closer," she said. "I want to see it up close."
With my cock and balls sticking out of my jeans I walked over to where Marilyn was sitting. To my surprise she reached out and took my hand off my swollen prick and spit into it.
"There, that will make it slicker for you."
At the same time she took my balls in her hand.
"Let me hold these out of the way," she said with a grin.
As much as my sister was trying to pretend this was a big joke for her she was also beginning t squirm in her sit.
I decided to go for broke. "I bet this would be even more fun if I could see your pussy!"
Marilyn let go of my balls and stood up. Shit. I thought I just blew it, but to my utter surprise she untied the thong and let it fall to the floor.
Marilyn's pussy had a strip of dark hair down the middle. The rest had been shaved so as not to hang out the side of the thong. She sat back down.
"Now what," she asked?
My cock was straining for relief and I had to stop jerking it least I blow my load and end the whole thing.
"Ummmm, can I see your clit?"
Without a word she placed both hands on the sides of her pussy and spread her lips. And there it was, the pinnacle of every man's desire. And as I stared at it I saw it grow. She was as horny as I was. Then without me even asking she began to rub her clit with her two index fingers.
"I'm warning you," she said, "sometimes I pee when I come."
I could hardly stand it, but I held off cumming to let her catch up.
Marilyn squeezed her clit between her fingers and jerked it up and down while systematically pushing her pelvis into her hands. I hardly moved my hands on my cock for fear of cumming right then.
Then suddenly my sister pushed her hips into the air and moaned, "I'm cumming now!"
As she spoke she began to piss. I wonder now if she had planned it because where I was standing she was able to piss a long arc into the air and have it land on my cock and balls.
As her pee drenched my hands she moaned out, "Come on my tits!"
I stroked my cock hard for just a few seconds when the first stream shot out bypassing her tits and hitting her squarely in the face. She didn't seem to mind in the least, but continued pissing; her piss mixing with my cum.
When Marilyn finally stopped peeing she gave a few more grunts and fell back on the recliner. The last of my cum was dribbling out of my cock as I collapsed in the chair next to her.
After a few minutes we caught our breaths enough to look at each other. We began to laugh.
I wondered where this was all leading to when Marilyn said in a very soft voice, "I wonder how that thing would feel stuck in this thing?" she pointed to her pussy...