My sister had always been a flirt. She flirted with my friends, my girlfriends, even me. Not that any of us minded. Sarah was a vision of beauty. She had bright blue eyes, a stunning figure and a great ass. Her tits were a little larger than average, and she kept her hair dyed a deep red. She didn’t mind showing all of this off either. Tight jeans and tight tops kept her assets on display all day, and she loved the power that she held over everyone.

I’d been having impure thoughts about my sister for a long time,and it’s hard to see how it could’ve been any other way. Sarah didn’t treat me like a brother; she treated me like I was just some guy renting a room down the hall from hers. She would run her hands down my chest in conversation; she would stand close enough to make most people uncomfortable, and she talked in a voice that made me melt. Over time I thought I’d get used to the effect that she had on me, that I’d develop some sort of immunity, but she managed to keep me suckered in just like every guy – and a fair few girls – she met.

Sarah was bisexual, a fact that she liked to remind me of occasionally, probably to perpetuate the fantasies she knew I had about her. I was too, though I’m far more attracted to women than men, and she teased me about it constantly, sending me pictures of her boyfriend stroking his cock, asking “Is he cute?” whenever I went out to meet one of my male friends. For the most part I didn’t care.

So there I was at 18, my sister 22. My parents were away for a week and Sarah was upstairs. My girlfriend Jess and I had been seeing a lot less of each other lately; I wondered if we would break up soon. The thought didn’t really bother me; whenever we fucked, I was mostly thinking about Sarah anyway.
Sarah came downstairs wearing a short skirt and a tight top. “Joe will be here any minute,” she said. Joe was her boyfriend. “Try not to stare at his ass too much.” Another joke about my sexuality. She sat herself down very close to me on the sofa and put her lips to my ear.
“You’ll be happy to hear that I intend to fuck him for the rest of the afternoon, so if you listen, you’ll be able to hear him moan.”

My cock twitched in my jeans. I did indeed find Joe incredibly attractive. He had olive skin and firm, well-shaped muscles. Sometimes I’d daydream about sucking his cock while I jerked myself off.

“Don’t be disgusting,” I said, trying to push the image out of my mind.

“What, you don’t want to hear?” she asked, dropping her voice to a whisper and getting even closer to my ear. “You don’t like the thought of him moaning as I ride his thick cock?”

Involuntarily, I let out the tiniest little moan of arousal, which she obviously delighted in exploiting.

“You do, don’t you? You want to hear him moan.” She climbed onto me, straddling me, and I could feel her pussy against my now rock-hard cock. “Or maybe,” she said, taking my face in her hands. “Maybe you like the idea of me getting fucked. Does your big sister turn you on?”

Without warning, she pressed her lips into mine and started grinding on me. Well, she’d taken this further than before; further than she should. But that doesn’t mean I was going to stop her. I opened my mouth to accept her tongue just as the doorbell rang. She slowly broke the kiss before looking me in the eyes and saying “He’ll be blindfolded. Maybe you want to come upstairs in a few minutes.” And then she got up, leaving me horny as fuck and frustrated, and answered the door. Joe stood on the threshold, looking as hot as ever. But at that moment, I couldn’t care less what he looked like. I’d received an invitation from my sister; an invitation to spy on her and Joe while they fucked. And I had every intention of accepting it, just to see my sister’s body.

Joe waved at me as he headed up the stairs and I nodded back. Sarah was just behind, and gave me a flash of her bare ass before following him. Now I knew I had to see her riding Joe’s cock as my own struggled against my jeans.

The following few minutes were the longest of my life. If I went up too early Joe might not be blindfolded, but I didn’t want to miss a single second.

Finally, it seemed the right amount of time had passed; I could hear Joe and Sarah fucking loudly, as well as the occasional sound of a face being slapped. Sarah liked it rough sometimes.
The moans grew louder as I climbed the stairs, and at the top I realised Sarah had left her bedroom door ajar for me. It was all I could do not to start rubbing my cock as I quietly pushed the door open...

Joe was lying lengthways across the bed, eyes covered and hands and feet secured by rope under the bed, while Sarah rode him, facing me. As the door opened, her eyes flicked up to mine and she smiled in the sexiest way I’d ever seen. She kept looking at me as she leaned back and started rubbing her clit, her moans growing louder.

“You want this pussy, baby?” she said, still looking straight at me.

“I want it so bad, whore,” was the response from Joe. I smiled and unzipped my jeans. He thought Sarah was talking to him, and not her little brother. I pulled out my cock, now at full mast, and let my eyes wander over both of their bodies as I jerked myself off.

Sarah silently beckoned to me as she fucked her hot boyfriend. “You wanna fuck this pussy? You wanna cum inside me? Is that what you want you dirty boy?”

“That’s what I want baby,” Joe replied, none the wiser. I approached them and I could smell the sex like a cloud around them. With her boyfriend unable to see, she pulled me close behind her and started jerking my cock while she pulled one of my hands down to her clit. The instant I touched her she screamed and dug her nails into my arm. Her hand on my cock moved faster as my fingers circled her wet clit.

“Ooh, yes baby,” she moaned, so loudly I thought the neighbours would hear. “That’s so good! You’re gonna make me cum...”

I watched Joe’s hips move up and down, saw his abs flexing with the effort. I could’ve cum right then and there, but it would’ve shot all over Joe’s toned stomach, and then he’d know something was up. The effort it took to keep my orgasm at bay was unvelievable, but luckily Sarah’s own orgasm tore through her and she collapsed onto Joe as she screamed, letting go of my cock.

I instantly missed the attention, but was pleased that I had time to wind down. I wouldn’t have been able to hold out any longer. Sarah and Joe were kissing deeply, and Sarah had begun to bounce on his cock again, both of them moaning into each other’s open mouths.

“I’m gonna cum baby,” Joe strained. I could tell he was seconds away from a huge orgasm, and wished I could see the cum shooting out of him.

“Oh, you want to cum, do you?” said Sarah. She then did something so mean I almost tried to stop her: she lifted herself straight off his cock and stood up.

“Ah, you fucking bitch!” he shouted. “Finish me off.”

“Not yet, lover boy. I told you I’d make you beg.”

“Please,” he was almost crying in desperation, and I sympathised. “Please let me cum, I’m begging you.”

Sarah had made her way over to me and was playing with my cock again while she said “Hmm...no, I think I’ll let you lie there while I get something to eat.” That evil bitch.

Joe whimpered, helpless to do anything while he was tied to the bed. I would’ve finished him off myself if I’d been given the chance, but Sarah led me out of the room, pulling me along by my cock. “Don’t go anywhere baby,” she said to the still tied-up Joe and smirked before closing the door.

As Joe groaned in frustration in Sarah’s room, the two of us walked quietly to my room, where she pulled me to her and we shared a deep kiss.

“I’m sorry baby brother,” she said with a pout on her lips. “You didn’t get to cum, did you?”

“I was so close,” I replied, half-knowing what was coming next.

“Well, I guess we’ll have to do something about it then.”

More to come, constructive criticism more than welcome!