Borderline

As her brother's cock settled all the way inside her, she felt it involuntarily throb as it was overcome with the sensation of being wrapped in her tight, wet skin. In response, she tightened the walls of her pussy to give her brother a loving squeeze. All those years of practicing were finally paying off. She smiled as she heard him sigh as well. Obviously, she had done the right thing.

Now there was a lull, as her brother lay fully inside her. Both of them seemed a little shocked by the pure pleasure of what they had felt for the first time. The twins were finally complete again.

After a few seconds, though, Melissa began to gently rock her hips back and forth. It did not take long for her twin brother to pick up on her silent urgings. He also began to rock back and forth, gingerly at first, his cock only moving a few inches inside her.

"Come on," she whispered.

That got his attention. He locked his eyes with hers, and she smiled. So that was it, huh?

"Come on," she said with more intensity, and he responded with more intensity, starting to take deeper and deeper strokes.

"Come on, big brother," she said breathlessly. She wrapped her arms around his neck as he poked her deeper still.

"Ah!" she gasped in pleasure as his pubic bone slapped against her clit. "Come on, fuck your sister! Oh!"

His balls began to slap against the bottom of her pussy as they found their rhythm. She wrapped her legs around him to let him get inside her even deeper.

"Come on!" she hissed at him. "Fuck me! Fuck me deep! Agh! Yes, that's it. Please, just like that. Oh! Fuck your little sister!"

It was a surreal sight in the moonlight. The slapping, wet sounds of sex were overlapped by Melissa urging her twin on. Her hands were wrapped around his neck tightly, pulling him to her, and her ankles were interlocked. Her hips rocked against his, fucking him right back. They reveled in his long strokes- he at the tightness, and she at the extended rubbing she felt in the sensitive ring around her slick hole.

After endless minutes of rubbing against each other, she felt him start to tense up. She squeezed down as hard as she could on his cock, trying to preserve him just a little longer.

"Melissa, I'm going to come!" he groaned.

"I know, baby. I can feel it," she hissed. "It's ok to come in me."

"Are you sure?" he asked.

"Yes, big brother. Slam me as deep as you can. I want to come too."

"But—"

"Slam me!" she demanded, bucking her hips hard against him.

In a slow motion moment of frenzied lust, the twins came together. He tightened his grip on her shoulders and impaled himself in her. She gasped, but did not flinch away. At the next stroke, she forced her hips up against him as hard as she could. The force splattered her freely flowing juice across both of their stomachs. Again they slapped together, grinding their hips in her fragrant cream. Again and again until on one stroke, his head press against her cervix. The sensation was too much for either one. Melissa began to cry out, and Mark quickly kissed her to stifle the noise. She responded by pulling on his ass to press his tip against her back wall as waves of orgasm ripped through her body. The involuntary rocking and shuddering tipped him over the edge. His cock swelled with as it began jetting cum against her very inside.

She was amazed, through the fog of her orgasm, at the heat of the cum pooling in her. Mark was lost in his own orgasm. Each writhed against the other, milking each other for every last second of pleasure they could create.

Mark was slumped on top of her, heaving like she was. She gave him a small shove to get him to roll over. He complied, and she gave an involuntary jump as his still-hard cock rubbed against her oversensitive clit. It was several minutes before either one could speak.

At the same time, they whispered, "Wow."

They laughed, then in tandem continued, "Jinx. Personal Jinx."

Mark smiled lovingly at his sister, and she returned the warm smile. The glow of the clock caught her eye as she lay intertwined with her brother.

"It's only 3:29," she told him as she laughed.

He laughed along with her.

"It's 3:30 somewhere in the world," he said. "And besides… it's only a technicality."

With those words, the twins fell asleep in each other's arms. And silently, one more minute ticked off the clock.