My Sister Is My Dom Pt.1 by Dirtywriter58

My step-sister, Fiona, and I had known each other for several years before my divorced mom and her single dad got married. Our parents were good friends before they married so although we weren’t technically a family, we did many family type things together, especially summer vacations at Fiona’s dad’s cabin on the lake.Fiona is three years older than I am, so she was never exactly thrilled to hang around with a younger kid during those pre-marriage outings, and once our parents did get married she avoided her little step-brother as much as I avoided my older step-sister. This is not to say we didn’t do things together, but we always sought out our own peer group when we could.

I was just starting high school when Fiona left for college. She rarely came home for visits, so we haven’t seen much of each other lately, but now she was coming for a long summer vacation. She’d just completed her third year in college and I had just graduated high school and turned eighteen-years-old.

Mom, dad, and I were already at the summer cabin when we heard Fiona pull her car into the pine-needle matted driveway. We rushed out to greet her with dad beating everyone to the car and opening the door. Fiona stepped out and hugged him tightly. “I’m glad to be home,” she said. “I’ve missed everyone so much.”

“We’re glad to see you too, honey,” Dad said. Then she hugged mom, who was almost in tears from joy. I stood back, waiting for the parental greetings to finish, and when mom finally let go of her, Fiona took a step toward me then suddenly stopped.

“Wow!” she exclaimed, “I was about to say ‘hello little bro’, but you’re not so little anymore.” She was right, when she had left for college I was barely the same height as she and very scrawny. Now, I towered over her five-foot-five frame and have put on quite a bit of muscle. “You’ve really grown,” she said while eyeing me with a suspiciously wry smile.

“You’ve changed too,” I said. Fiona was always a little heavy in high school, and being a rambunctious tomboy, never paid too much attention to her appearance. All that seems to have changed, she wore a halter top without a bra and I could see that her breasts were firm and her nipples protruded enough to be noticeable. Her arms were slim, shoulders softly rounded, and her waist was a perfect hourglass shape. She wore a pair of running shorts which showed she had a flat, taut abdomen and nicely shaped well-muscled legs. Her hips were slim and ass well-rounded. I thought, damn, my step-sister is hot; but out loud, I said, “You look good.”

We exchanged a cursory hug and all went inside. The afternoon and evening was spent reminiscing, catching up on new events, and eating dinner. I was eyeing Fiona the entire time, amazed at how good she looked. Every once in a while, she would catch me looking and grin back at me with the same devilish look she had given me earlier.

The next morning was spent packing the car. “Your mom and I have to return to work for the week,” dad informed us. “We’ll return on Saturday, so you two are alone here the entire week. Here are the rules.”

“Daddy,” Fiona whined, “I’m twenty-one. I don’t need rules to act like an adult.”

“Since you’re twenty-one, you’re in charge,” dad retorted.

“Now I have a problem,” I interjected. “I’m eighteen; I don’t need my sister to look after me.”

“Stop it, both of you,” dad said sternly. “Here are your rules. No parties. I don’t want a group of strange kids running around the place.”

“Out here, in the middle of nowhere. Maybe we could round up a group of antelope, but we’d never be able to round up enough people for a party,” I explained. Dad ignored me.

“No swimming, boating, or hiking alone. You look after each other.”

“Yes, daddy,” Fiona said appeasably.

“Yes, sir,” I said. We finished loading the car and they drove off while Fiona and I waved.

Fiona turned toward me as they drove out of sight. “Matt, let’s go swimming,” she said excitedly.

“Now?” I questioned.

“Yes, now,” she demanded. “Dad said we have to swim together, so go get your swimsuit on or I’ll call him and tell him you won’t abide by the rules.”

I shrugged my shoulders realizing this week is starting out to be a harrowing experience for me. We went inside, changed into our swimsuits, and I followed Fiona out to the lake. She wore a tiny fluorescent orange bikini. She could be seen a mile away against the backdrop of browns and greens in the woods surrounding the lake. I watched her ass wiggle as we walked to the end of the floating deck. It appeared incredibly firm and there was a definite rocking action as she swayed. I was beginning to get aroused.

I tossed my towel to the deck and went to the edge to dive in the lake. Just as I was about to dive in, Fiona grabbed my baggy swimsuit and pulled it down to my ankles. I was shocked and stopped myself mid-dive to turn and see what she was doing, but as I had already committed to the dive, I fell sideways into the water. Fiona jumped in right after me and finished removing my shorts before I even had a chance to recover from the plunge.

“What the hell are you doing, Fi?” I shouted after getting my head back above the water.

She twirled my swimsuit above her head and tossed it onto the deck. “I wanted to see what you looked like without clothes,” she answered.

I splashed water at her and said, “You’ve seen me naked before.”

“Yes, but you’ve gotten bigger since then, a lot bigger.”

“Well, I hope you got a good eyeful,” I said sarcastically.

“I got a peek. I’ll get an eyeful when you get out of the water.”

“I’m not getting out of the water while you’re here.”

“You heard what dad said, no swimming alone. If you’re in the water, I’m here with you,” she admonished.

“So I’m naked while you’re fully clothed.”

“In this tiny swimsuit, you’ve already seen just about all of me.”

“Not the same,” I complained.

“Alright, here,” Fiona replied. I watched closely as she took off her bikini top. She raised her arms above her head to toss the bra onto the dock and that made her tits stand out. They were gorgeous, absolutely perfect, with a smooth peaked shape and pencil-eraser sized nipples that stood proud and hard from the cool lake water. “Are you happy now?” she asked.

“No,” I lamented, “you still have your bottoms on.”

“You don’t get to see my cute ass, at least not yet; maybe later.”

“Then let me get a look at your tits.” I swam over and put my hands on her waist to raise her out of the water and expose her breasts. As I lifted her up, she reached under the water and cupped my genitals in her hand. I was startled at how aggressive she was acting so the expression on my face must have been hilarious because Fiona smiled widely and started giggling. I didn’t get much of a look at her tits because I immediately pushed her away so I was out of her reach.

“What’s the matter, are you shy, little bro?” She said tauntingly.

“What are you up to, Fi?”

“The water’s cold,” she said as she began to swim back toward me. “I wanted to make sure you weren’t getting a chill.”

“That’s it, swim time is over. There’s something wrong with you today.” I spun her around and pushed her toward the ladder. She swam to it, soundly kicking me between the legs as she started out. I groaned from the sharp pain and then watched as she climbed out onto the deck, her smooth, wet skin glistening in the sunlight as the water ran off her body. She wrapped the towel under her arms and around her torso, covering her chest before turning around to watch me get out of the water. I struggled up the ladder, my balls hurting from the kick and I was embarrassed that my sister was staring at my exposed genitals. I wrapped the towel around my waist and proceeded to the cabin.

“I’m taking a shower,” I called out as I went up the stairs. The lake water had been cold so I ran a hot shower, got in, and began shampooing my hair.

“Matt, do you need anything?” Fiona called to me from the hall.

“No, Fi, I’ve got everything I need,” I shouted while rinsing my hair.

“Are you sure?” Fiona asked, her voice no longer coming from the hall, but coming from within the bathroom. I moved my head out from under the running water and opened my eyes. Through the water-streaked glass shower door, I saw Fiona, naked, in the middle of the room. She looked magnificent, her slender build beautifully curved, her smooth skin unblemished, and her pussy shaved bare. She shook her head, tossing her sandy blonde hair from side to side. “How about me?” she asked.

“Fi, what’s gotten into you?”

“I’m horny,” she replied as she walked over and opened the shower door.

“I can see that,” I concluded.

“And I need a shower too. Dad said no going in the water alone.”

“He said no swimming alone.”

“Minor detail,” she said jokingly. “He meant we have to watch out for each other, so that’s what I’m doing. You wouldn’t want him to find out we weren’t looking out for each other.”

“What have they been teaching you at that college?”

She stepped into the shower and closed the door. “They taught me that since I’ve got the pussy, I make the rules.”

“So what have you been doing, sleeping with half the student body?”

“I’ve only slept with two people the whole time. I had a boyfriend for about six months and I slept with one of the professors a couple of times. My boyfriend was on the swim team and he was built like a granite mountain. The professor was older and had a small dick, but he had big ideas. I learned a lot from him.”

“Did you learn that it’s okay to come-on to your brother?”

“If I want to, yes; besides, I saw you leering at me yesterday. I know what you were thinking.”

“Thinking it is one thing, Fi, doing it is another.”

“Little bro, sit back, relax, and let it happen. I promise you’ll enjoy yourself.” She picked up the bar of soap and began to lather my genitals, slowly rubbing the bar over my cock, around my groin, and between my legs. I began to get an erection and she continued to soap me until I was fully erect. She handed me the soap and stroked my sudsy cock with one hand and massaged my groin with the other. “I have to start calling you big Matt. You’ve got the biggest dick I’ve ever handled. This is going to be fun.”