Conditioned Response

She sat back on her knees between his legs in the aftermath, savoring the last of his semen and looking down at his toned body. It made her smile every time she saw that deeply satisfied look on his face. Maddie started shifting her weight, preparing to get out of his bed, when she saw that he was getting hard again. She held perfectly still and looked at his delicious, swelling cock. Then she looked up at his face, watching his pupils move lazily behind his eyelids. She had never sucked him off twice in one night before.

She moaned softly as his hardening cock slid into her throat again. "So good," he murmured again, and her pussy exploded when his hips thrust upward.

* * *

It was a very minor oversight that changed everything. There was a very small pinhead-sized light just below the camera lens atop both of their monitors. Every time the camera came online, the light would come on for three seconds. When it shut down, the little bulb flashed three times. Maddie had used her camera to Skype with fellow physics enthusiasts and some other students, but had not used it much over the past three months. Because her focus was always on the little Skype window when her camera came on, she had never noticed.

She was using the camera in her brother's room every night to make sure he was asleep before she entered his room. She was very careful every time, and her brother was a deep sleeper, so he never had a clue what was happening. He just thought he was having amazing dreams.

After three weeks of deep-throating her brother every night, Maddie was completely addicted. There was no adverse effect on her life; if anything, she was more alert and focused when she went through her daily routine of classes, labs and tests. One warm May evening, though, all of that changed.

Maddie was looking forward to her nightly visit when she turned on her computer. She turned on the camera in her brother's room and was disappointed to see that he was still awake. She watched him for a minute, and then turned the camera back off. She looked at her clock before sliding back into bed, figuring she would check again in an hour.

Todd was lying awake in his bed when he caught a tiny red flash out of the corner of his eye. By the time he turned his head to find it, the light had gone off. He was ready to dismiss it as imagination when he saw the little red light flash three times. It was coming from his monitor. That seemed odd, so he slid out of bed to figure out what had happened.

He sat at his desk and wiggled the mouse to turn off the screen saver. The monitor brightened, and he finally noticed the little red light below the camera atop his monitor. That's weird, he thought. I've never even used this camera.

Todd moved his mouse all over the screen, highlighting and clicking on several icons. Nothing seemed out of the ordinary, until he moused over a little icon in the bottom right corner. "Remote access enabled" popped up in a little bubble. He felt a chill as he read it twice.

Someone had hacked into his computer!

It never would have crossed his mind that Maddie might have done it. Instead, he pictured some gross, hairy, overweight old guy perving on him as he spied on Todd in his sleep. Todd immediately pulled on a pair of shorts and a t-shirt. He sat back down at his computer, but he was not tech-savvy enough to figure out how to disable the remote access. He went back to bed, but he was deeply disturbed and could not go back to sleep.

It got even worse—an hour later, the little light came back on. Todd rolled out of bed, but the little light flashed three more times and the camera was off by the time he got onto his computer again. He was shaking when he turned the computer off. He turned on his bedroom light so that he could see and unplugged the power strip that served for his computer, monitor and phone charger. Unfortunately, it also turned off his alarm clock.

Back in her room, Maddie groaned in annoyance. Not only was Todd still awake, but he got up. She figured he was going to the bathroom, and that he would be awake for a while. It was a school night, and it was very late. She would not get her fix of brother cum tonight. Maddie fell asleep after rolling around for a half hour.

Their mother remarked the next morning, "Are you guys alright? You look like you barely slept."

"I just couldn't sleep," Maddie replied with a shake of her head.

"Me neither," Todd said, yawning.

It was a Thursday, so Maddie took the bus home after school. Todd was waiting for her. "Maddie, I need your help," he said quietly. "I think I have a real problem with my computer."

Maddie yawned, covering her mouth with the back of her hand. It had felt like an incredibly long day. She had been out of sorts all day, and now felt mentally exhausted. "Excuse me," she said after the yawn. "I am just wiped out, Todd. I really need a nap, but then I'll be happy to have a look at it."

"Thanks," he murmured. He immediately felt relieved. Maddie was a genius. She would figure it out. He could actually feel his shoulder and neck muscles relaxing. "I didn't know I was that tense," he muttered to himself. Of course, his eyes were still glued to his sister's sweet bottom as she disappeared into her room.

Maddie stripped out of her clothes, rubbing her tender breasts after removing her uncomfortable bra. "I really need to do something about that," she said out loud. For once, her panties were not damp at all. She was so tired that she slid into her bed wearing nothing but those panties, falling asleep immediately.

Todd was watching television in the living room. He had finished the little homework he had before Maddie had arrived, and he was fidgeting as he watched some cartoon reruns. He got up from the couch and went into his room. He plugged the power strip back into the wall and restarted his computer and monitor. He realized that his alarm clock was flashing 12:00, and set the correct time as he watched his computer go through its start-up sequence.

He had just left the thing sitting on for so long that there were a lot of updates that it ran automatically. Every one of those made Todd's eyes narrow with paranoia. He had no idea what most those programs were. After his computer was finally through with all of the start-up programs, he sat and moved the mouse down to the bottom right corner. "Remote access enabled."

"Shit," Todd hissed.

He got up and paced around for a while. Finally, he decided to see if Maddie was awake. He went to her bedroom door and tapped on it. "Maddie...?" The door swung open.

Todd's eyes went wide when he saw her. Maddie was asleep, but she was slurping on her thumb noisily and moaning. Todd had seen infants and toddlers suck their thumbs before. This was not the same thing at all. His sister was giving a blowjob to her thumb. Not only that, but she was thrusting it in and out of her mouth while her lips and tongue worked it over.

Todd was watching with his mouth open wide. He wasn't even aware of each step he took into his sister's room. However, he was aware just how hard he was getting as he watched her. She was barely covered by a sheet. He could not help himself. He lifted the sheet. "Jesus," he whispered.

Maddie's perfect breasts shook and her nipples were rock-hard. Todd's mouth watered as he looked at them. Then his nostrils flared. His eyes traveled down her body, and his breathing quickened. She had a hand pushed into her panties. It was making its own wet noises to compete with the slurping her mouth was making. She shuddered and moaned around her thumb. "Delicious...mmm...cock."

Todd's cock shook in his shorts. It was as hard as it had ever been, pushing his shorts straight out in front of him. For a fleeting moment, he seriously considered pulling Maddie's thumb from her mouth so that he could feed her his dick. As aroused as he was, he still felt ashamed for thinking about his sweet sister that way. He shakily retreated from her room and closed the door firmly.

He stood there, staring at her door and breathing heavily, for almost a minute. Then he went into his bathroom and masturbated until he shot cum all over his sink. He felt shame afterward. He had been imagining Maddie sucking his cock the entire time.

* * *

When Maddie woke up from her nap, she had completely forgotten that Todd had asked about help with his computer. Todd had managed to forget as well, since he was preoccupied. He was struggling NOT to picture Maddie sucking dick. Unlike his sister, he had not had a nap. After dinner, he was exhausted. He excused himself and went to bed.

So tired was Todd that he completely forgot about his "hacked" computer. He stripped and slid into his bed, falling asleep immediately. It was early evening, and Maddie watched television with her parents before going to her room to work on her studies for a few hours.

"Goodnight, Maddie," her mother said from her bedroom door.

"Goodnight Mom. Goodnight Dad," she replied, looking up briefly from her screen to smile at them.

She smiled again when she heard them close their bedroom door. It was a Thursday night. She had no school tomorrow, and looked forward to a nice long session with her brother's cock in her mouth.

* * *

Todd was having a lucid dream. He was asleep, but in his darkened room, he felt the blaze of a bright red light and knew that he was being watched. He moaned but wasn't able to wake up. The light flashed three more times. In his dream state, it was a tremendously bright flash—filling his room with a hot red glare each time. His body relaxed a bit when it finally stopped, but then he heard someone enter his room.

He felt guilty as he dreamed of his sister. She was sliding into his bed, moaning as her wonderfully wet mouth took his hard cock to the root. Todd knew that he was dreaming, but it felt incredible. In the dream, his sister was turned on just from sucking his dick. She moaned ecstatically when his hips thrust up toward her face. He could practically feel her shaking as she got off. It was too much for him, and he groaned as his cock exploded. Those silky throat muscles just milked him dry. It was without a doubt the most intense dream he had ever had. It felt so real that he thought he could even smell her aroused pussy.

"Oh, Maddie," he moaned.

Maddie froze. Her eyes were wide as she looked up at her brother. His eyes were half open, and he was looking right at her!

She had been certain that he was asleep when she came in. Had she been too loud? Was she sucking him too hard? Todd smiled and let out a long breath. His pupils were still moving languidly, and his eyes closed. His breathing was slowing to its normal relaxed pace; just like it did every night he came in her mouth. This time, though, he never went soft in her mouth.

Maddie watched him carefully as she started sucking him again. He was definitely asleep. She shook when the reality of what had just happened hit her. Her brother was dreaming about her! Maddie's arousal was at a fever pitch as she felt her brother fucking her tight throat. At some level, he knew he was fucking his sister's mouth, and he was loving it. He moaned, "So good," again and again as he pumped his cock in and out of her.

Each time he said it, Maddie's wet pussy gave a twitch. She came like crazy when he once again unloaded his balls down her throat.

* * *

Unlike the previous dreams that he could not recall, Todd woke up with every detail of last night's erotic dream crystal clear in his mind. He felt guilty as hell for dreaming about his sister that way, but...God, that had been incredible! He was guilty and aroused all through the day. At breakfast, he could not help but let out an aroused breath when Maddie licked her lips.

He wondered if he had been dreaming about his sister for the past month. He turned that over in his mind before dismissing it. Until he had seen her napping in her bed yesterday, he had never thought about his sister that way. Oh, he had admired her sexy body a lot lately, but he certainly never thought about her sucking his dick.

Todd went from class to class, with that dream replaying over and over in his mind whenever his attention was not focused elsewhere. In his fifth period English class, he suddenly sat bolt upright in his seat. It had been a dream, right? That hadn't actually happened?

It didn't seem possible, but...

The more he thought about it, the more he realized it was possible. Just extremely unlikely. What could have possibly happened to lead his sister to start sneaking into his room to suck his cock? Once again he replayed the dream. Maddie had really gotten aroused from sucking his dick. She had come, hard, when he had fucked her throat and again when he came in her mouth.

That wasn't a natural response. Something was wrong there. It was the kind of thing a guy would dream about, but it couldn't ever happen. In his mind, he could hear himself moaning 'so good' over and over. Every time he did, she would moan and shake in response. "So good," he whispered. He realized that he had said it out loud, and sat up to pay closer attention to what the teacher was saying.

When he got home from school, he was once again delighted to see his sister bounding over to give him a hug. Her breasts bobbed beautifully and he loved seeing her hard nipples through her t-shirt. She looked up at him after he hugged her back, and she seemed to be looking for something in his eyes. He kissed her on top of her head. "I'm going to go change," he said.

That look she had given him...Todd stripped and pulled on his thin jogging shorts and a tank top. It really felt to him like she was nervous. Boy, it was so unlikely, but he was starting to believe it. Maddie was sneaking into his room at night. He shook his head. No...

His eyes shot open then. If she was sneaking into his room, then was she the one who had hacked into his computer? He wanted to be offended, but just couldn't do it. None of this made any sense. What the hell was going on? He left his room and walked out to the kitchen. He did not look directly at his sister, but he could see her checking him out from the corner of his eye.

He grabbed a cold sports drink from the refrigerator and opened it as he walked out to the living room. Maddie turned on the couch and smiled up at him. He smiled back and then took a big sip. He could not help it; he had to try...

"Mmm. So good," he moaned after that sip.

Maddie's head jerked over to look at him, and her breasts heaved under that thin t-shirt. Her eyes glazed a bit, and her mouth opened. She let out a soft moan. Then her eyes wandered down to his crotch. Todd took two steps toward her, and her eyes followed his hardening cock as it moved from side to side. He took another long sip as he looked down at her.

Damn. It was true. Maddie had snuck into his room and sucked his dick last night. Judging by her reaction, this had been going on for some time. He could not help but get aroused at that thought. Maddie's pupils widened as she watched him get harder.

Todd swallowed the cool sports drink. "So good," he repeated softly. Maddie moaned as he took another two steps toward her. He was standing in front of the couch facing her. It still surprised him when she slid from the couch to kneel in front of him. Her mouth looked so inviting as she opened wide and licked her lips.

Unlike his sister, Todd was familiar with mental conditioning and the psychology behind it. Clearly, his sexy sister was showing a conditioned response. He wondered how she had managed to get herself mentally conditioned like this. She was obviously aroused and wanted to suck his dick. He felt a little guilty, but he really wanted to watch her do it.

Todd took one more sip and then set his sports drink bottle on the coffee table. He turned back to Maddie, noting how her eyes never left his hard cock the whole time. He stepped right up to her, so his cock was practically touching her lips. "So good," he said. Maddie moaned as she lifted the leg of his shorts out of the way and urgently swallowed her brother's hard cock.

Once she started sucking his dick, Maddie's mind cleared just enough for her to realize what she was doing. Her eyes opened wide, just as her throat had done seconds earlier. She looked up at Todd's face above her. He was watching her suck his cock!

She felt like she needed to stop, but couldn't. Somehow, she felt the need to apologize for what she was doing, but she couldn't stop swallowing her brother's delicious cock. She also could not tear her eyes away from his. Clearly, he was turned on as he watched her. Maddie shivered as her wet pussy sent waves of pleasure through her.

Todd licked his lips as he watched his sister come. "So good," he moaned again. She almost whined around his dick when he said it, and then he put his hand on the back of her head. Maddie came like crazy when her brother started fucking her throat right there in the middle of the living room.

The last of Todd's guilt melted away when she slid her hands up the back of his legs and squeezed his ass. It already felt amazing to drive his cock into that eager, tight throat. Her hands pulled his ass toward her, urging him to really let himself go. He knew that she wanted this to happen, maybe even more than he did. She wouldn't be mad, like Jasmine had been.

Todd drove his hips forward, and both of them moaned each time he did it. He let himself go, fucking his sister's sweet mouth and enjoying the incredible sensation. All too soon, he was at the point of no return. When his cock swelled up, instead of choking on it his sister moaned deliriously. Her hands pulled him tight into her and her lips locked around the base of his shaft. His balls were planted firmly against her chin when they clenched up.

"Oh, Maddie!" he cried out. She was simultaneously sucking, licking and swallowing as his cock exploded in orgasm. He watched wide-eyed, still scarcely able to believe it, as his sexy sister came like crazy while swallowing his cum. His legs shook with the force of his orgasm. He felt weak and had to sit down. Maddie followed him all the way, sliding over to kneel between his legs when he plopped down on the couch.

She nursed the rest of the cum out of him while he sat there and watched. It took a while for him to catch his breath afterward, but she never took her mouth off of his cock until she had drained every drop. When she finally released him, she sat back and licked her lips. She was clearly savoring the semen in her mouth before she swallowed the last of it.

Todd patted the seat next to him on the couch, and she rose from her knees and slid next to him. "How did this happen?" he asked softly.

Maddie was ashamed to admit that she had spied on him, but he rubbed her back and said, "It's okay. Tell me what happened after that." She did not leave anything out. It blew his mind that she had trained her gag reflex away the way that she had. He looked at her face, but her focus was on his crotch. He had gotten hard again when she had described the process of fucking her throat with that carrot.

When she finished telling him everything, she looked from his lap up to his face. "May I?" she breathed.

He nodded. "Go ahead."

He could only shake his head when she murmured "Thank you!" and dove onto his cock again. For once, she did not have to worry about being quiet, and Maddie noisily devoured her brother's throbbing dick.

Wow, Todd thought as he watched her head bobbing enthusiastically in his lap. It felt even more amazing than it looked, and it looked pretty fucking amazing. As he sat back and enjoyed the fantastic blowjob, Todd realized that his sister really did not understand what had happened. She described her "obsession" but did not see the stimulus-response training that had been going on the whole time.