In the space of some 20 or 30 seconds, a million nervous impulses did what they were designed to do and did it flawlessly. And, in the space of only 4 or 5 seconds, even more millions of healthy, viable sperm cells were transported from one human being into another.
A miracle of nature had taken place in the space of a few breaths, and even fewer blinks of an eye.
Debbie felt, on some level, the rush of wet warmth that flowed into her body from her brother's penis. She was instantly addicted to the feeling. She was addicted before she had any conscious thought of what was really happening, or the consequences of those actions. On a purely metaphysical plane of existence, she knew she had found the thing that made her the happiest she had ever been thus far in her life.
Robby's experience was a bit more tortured. He knew exactly what was happening before it actually happened. He knew he was about to cum in his sister, and that there was nothing in the world he could do about it. He knew that even if he jerked his prick out of her, he couldn't do it before he spermed her pussy. In his mind's eye he knew he was going to fill his sister's belly with life and the electrons bouncing around in his brain visualized his emission as tiny full-formed fetuses being injected into her womb, where the thousands he saw would grow and burst from her body, destroying her like some alien plague.
Even as he felt the explosion of ecstasy that went along with his orgasm, he felt the misery of having ruined his sister's life. He berated himself, admitting that he knew better than to let her bully him into doing this thing. At the same time he felt his body insist that he stay right where he was until the last feeble clench in his groin expelled the last few straggling sperm cells from his body into hers.
Then, feeling completely miserable, he collapsed on top of her.
They lay there gasping for breath for a few minutes. Robby rehearsed in his mind the various ways he could apologize to his sister, who would now probably hate him for the rest of her life. He felt her hands come to his waist, and expected her to push as her angry outbursts began.
Instead her hands stroked along his sides, and up onto his back, and then down to his buttocks.
"Oh thank you Robby" she sighed. "Thank you so much."
Robby was stuck speechless.
Debbie squeezed him with her arms. "I completely understand why Mommy wants to do that now."
Robby found the energy to push with his arms, so he could look at his sister's face. Perhaps the 'alien invasion' had altered her already.
"I fucked you," he said. It was hard to tell if that was a question or statement. The words sounded harsh in his own mind, but that was how he characterized what had happened.
She just looked up at him adoringly, her eyes big and liquid brown suddenly.
"I wasn't supposed to do that," he croaked.
Debbie's hands left his sides, where they had come to rest. She grasped his head gently and pulled him down for a kiss. When it was done she let him go.
"When do you think you'll be able to fuck me again?" she asked. "You didn't go nearly as long as Mommy and Uncle Robert go."
Robby looked at her incredulously. He tried to roll off of her, but she gripped him and rolled with him until they were again lying side by side.
It took half an hour, but they talked about what had happened, and how each of them felt about it. Robby learned that, not counting the dangerous nature of the transfer of body fluids, he had done nothing but please his sister. She had already forgotten the pain and discomfort she had felt initially. She didn't care about the fact that he might have made her pregnant. She would care later, but she was still in the grip of the chemicals a woman's body produces during an orgasm that are designed specifically to encourage her to lie there afterward and let all that nice sperm soak in completely before she gets up.
In the end he insisted that, if they did this again, they had to do it only at times when she was unlikely to be fertile and that they had to try to find some way to acquire some rubbers. She, on the other hand, insisted that she would be extremely unhappy if he tried to keep her from enjoying this new thing they had found together, and that it would happen again or he'd be sorry.
While it sounds like they argued, it wasn't really like that at all. It was more of a situation where each pleaded his or her case about what they wanted the future to be like. As with most teens, they couldn't see very far into the future, and their plans were, for the most part, short term. It was impossible, lying there in the afterglow of sex, even if it wasn't 'good sex' in a classical sense, not to give each other little loving touches and kisses.
Once they had said what they felt the need to say, they kissed some more. It was comfortable lying there together. Their speech got less and less focused and, eventually, they drifted off to sleep in each other's arms.
That's how Ramona found them when she broke her routine and came home for lunch for only the 3rd or 4th time since she'd taken her job at the bank.