Well let's just see...

She awoke in the night to a flash of lighting and something hard poking her. What was that? Thunder followed the lightning closely and she remembered: oh right, Brad. But what was that? She felt around and the… oh god! He must be having a wet dream! It was his hard cock poking her ass lightly. She withdrew her hand quickly, but not before a thrill went through her pussy. God, it felt big, as thick as her wrist. Her pussy was rapidly warming, not really satisfied from earlier. Maybe she could just touch it a little? Her hands lightly touched it through his pajama pants, her pussy tingling constantly. Fuck, it is big. At least eight inches, in addition to his girth. Her pussy was leaking continuously now, the tingling warmth overtaking her conscious mind for a moment.

Damnit, no, this was her brother! She slipped out of bed quietly and went to the bathroom. She quietly and quickly rubbed one out again on the toilet, but it only helped a little, the tingling warmth was gone and it just didn’t feel very good. What was happening to her? She just needed to get back to bed and get to sleep. Things would be so much clearer after a good night’s sleep.

Newly renewed in her convictions, she slipped back into her bedroom and… oh god… he had rolled onto his back and now his hard cock had slipped just a little out of his pants, just the tip. It looked delicious, it was even leaking a little precum. He must be having a really good dream. Her mouth watered as the tingling warmth started again. What was going on? Was this really her? Was she really thinking about licking that delicious, big cockhead? Was she really thinking about taking her brother’s big, hard cock in her mouth and sucking it until he came? No, no, that wasn’t right but… but maybe she just needed a closer look…

She walked, nearly ****, to the side of the bed and got on her knees. The tingling got more intense with every step, and on her knees with the smell of her brother’s precum in her nose she nearly came without even touching herself. God it smelled so good. She could see a big drop of precum right on the tip, just like it was waiting for her to lick it… and… oh fuuuuuuck….. Possibly the strongest orgasm she ever had ripped through her as the taste of his precum hit her tongue! Fuck, it tasted amazing… she just had to have it!

Throwing caution to the wind she pulled down his bottoms and swallowed her brother’s cock. Fuck it tasted good, and she loved the feeling of his hard member in her mouth. It was delicious and so big in her mouth! The feelings in her pussy were at a fever pitch now. The only thing she could think about was this amazing cock in her mouth and the feelings in her pussy. She started moving her mouth up and down this amazing cock. Brad moaned a little but Katherine was in her own world now, her senses filled with the vibrations in her pussy and the cock in her mouth. She got faster and faster on his cock, throwing caution to the wind, feeling a pulse in her pussy every time his cock pulsed and released precum into her mouth. Fuck it was tasty.

He was getting closer to cumming, she knew it. His cock was starting to swell a little, and his hips were starting to buck. Brad moaned, and Katherine knew things were going too far, but she just couldn’t stop! She felt too good. Brad moaned as thunder cracked outside and his cock swelled, filling her mouth with hot, delicious cum as her pussy exploded. She automatically swallowed as the feelings in her pussy continued, making her cum again and again.

When she finally came down to earth, she realized her mouth was still on his (still hard?) cock. She immediately backed up, and looked up to his face where… oh shit! He was looking right at her with a… was that a smile?

“Oh god, Bro, I’m so sorry, I don’t know what came over me, I-”

But he cut her off by grabbing her and pulling her slight frame onto his on the bed. His hard cock was near her pussy now, and she started feeling vibrations in her pussy again. He kissed her hard.

“Katherine, don’t be sorry! I love you! You made me feel so good.”

The rubbing of his cock and the vibrations of her pussy were quickly making her lose control again. What was happening! She never felt this way before! But oh, god, does his cock feel good. How would it feel in her pussy…

“I love you, Katherine. I’m so glad you came to me. Do you want… do you want to go further, Katherine? Do you want to fuck? It only makes sense.”

Katherine’s pussy once again exploded, her pussy soaking through her panties onto Brad’s cock. I guess.. I guess I do want it, she thought. She nodded as she came.

Brad smiled again, and then flipped them both over so he was on top of her. She also squealed but he covered her mouth with his as he slipped her panties aside, placing his big cock right at her entrance.

“Oh god, Brad, but you’re… you’re my brother!”

Just then his cock made contact with her pussy, and yet another orgasm ripped through her, and destroyed what was left of her hesitation. Brad, ever the kind brother, though, checked in.

“Do you want to stop, Katherine? We don’t have to do this.”

His cock belied his concern, though, as it pushed against her vagina, seeking to stretch it open, as another orgasm overtook Katherine.

“Oh god, never mind Brad, fuck me! Fuck I’m so horny!”

He grinned a sly cheshire grin before jumping off her, to her confusion.

“Wait, Brad, what? Oh.. OH YES!”

Instead of sliding his cock into her, he slid his tongue in! He went down on her like a pro, and Katherine felt like her pussy must be burning him, based on how incredibly hot it was! She was leaking like a faucet, too, and her brother gamely licked up her sweet juices as she got closer to coming again. Then, just as she was cresting the hill, his finger made it’s way into her asshole! It slipped in easily with the help of that pussy juice and she was about to object when the vibrations in her pussy got even stronger and she crested into yet another explosive orgasm! Fuck, who taught her little brother how to treat a lady this well! Her objection to the finger in her ass was lost as she went over several successive waves of orgasm, each one peaking as his finger dove into her rear hole. I guess I like anal after all, she thought!

Then, as quickly as he had left, he was once again on top of her, his big, thick cock once again spreading her pussylips open. She bucked against him, trying to swallow him. How did this happen? How did she turn into such a slut for her brother? And most importantly, did she care?

“Oh fuck bro, please fuck me, i need your big cock!”

The vibrations in her pussy were overwhelming. She knew, just knew, that his cock would help!

Again with that grin! He deftly avoided his cock sliding into her as she bucked and responded.

“Are you suuuuure, sis? Sure you want to cross this line? If we do, we can’t go back! You’re going to be my sister slut after this!”

“Fuck, bro! Fuck fuck fuck yes! Fuck me! I don’t care, I want to be your slut! Just give me that big cock!”

His grin changed just a bit, to one of victory. Not that Katherine could really see it, though, because her eyes were closed in ecstasy as her brother’s big, hard cock slid into her wet pussy. God it was so fucking good! She was cumming in moments, her pussy feeling every inch of his thick shaft as it slid into her.

It was amazing! She could feel her pussy stretch around his cock as it slid in and out, she could feel how wet her pussy was as she thought about how her brother, her BROTHER! Was sliding such an amazing specimen into her tight little pussy. She crested wave after wave of orgasm as his member fucked her hard and deep, and he whispered into her ear.

“Do you like that, sis? You like getting fucked by your brother? You want to do this every night from now on?”

Katherine mewled and nodded as best she could, barely aware of what he was saying over the constant orgasming. This was the best sex she’d ever fucking had, and it was her brother! She could only barely wrap her head around it, but she knew it wouldn’t be the last time.

Her brother pulled out, to her moaning protestations, but quickly flipped her over and slipped back inside her. His hands again went to her asshole and this time she didn’t even try to protest, relishing the new feeling as his finger slid easily into her. She felt like the vibrations in her pussy got even stronger when he did, and she rode them to yet another wave of continuous orgasm as he fucked both her holes. Her mind briefly wandered to what it would be like to be double penetrated, then to what it would be like to be double penetrated by her brother and daddy, and nearly passed out as the biggest orgasm yet ripped through her. But she quickly corrected herself, sex with her brother was entirely different than her dad, that was going too far.

She wasn’t sure she totally believed it, though.

But she was distracted as Brad once again pulled out of her pussy, as she quickly felt his cock press into her rosebud. Was he going to fuck her ass? Did she… want his to fuck her ass? The feelings in her pussy answered for her, and she moaned lustily.

“Fuuuuck, yes Brad. Fuck my ass! Fill my virgin ass with your lovely cock!”

Brad even seemed taken aback by this and paused a moment.

“You’ve never been fucked in the ass? You sure you want this, sis?”

Her moans turned to whines at his reticence.

“Mm, come on bro! Yes! I just want your cock in me pleeeease fuck my ass!”

“All right, sis, I guess you’re literally asking for it!”

And with that he pushed forward, his cock pushing into her tightest hole. God, it felt absolutely amazing. It felt weird, she couldn’t lie, kind of like pooping in reverse. But at the same time, oh wow did it feel good. The pressure of his cock spreading her asshole, and filling her up was truly incredible. And the intense vibrations in her pussy and taboo nature of the act was just making her whole night one long orgasm.

With all the fucking before this, and he asshole clenching continuously on his cock, Katherine’s brother didn’t last too long in her ass.

“Oh fuck, Katherine! I’m going to cum… I’m going to cum in your ass!”

She was, one last time, about to object when a last overriding wave of vibrations in her pussy sent her over the edge and all she could do is moan happily as she felt Brad’s thick cock swell even more and start releasing thick, hot cum into her once virgin ass. Her brother’s cum! Her body jerked again as that thought crossed her mind. After a moment with a few more last, spasming jerks from her as the last of her orgasms subsided, her brother slowly slipped from her asshole.

“Fuck… brad… that was… amazing…”

Brad flopped down next to her, breathing heavy.

“Sis, that was… so amazing. You’re so hot! I hope we do this a loooot more.”

Katherine’s pussy thrummed at this, but just a little, as she happily drifted off in her orgasmic haze, feeling delightfully sore in all her holes, and with the taste of her brother’s cum on her lips.

The next morning was bright, with no sign of last night’s storm. But there was one aftershock of last night, as Katherine woke to the musky smell of Brad’s cock as he pushed it against her lips. Not usually one for such wakeups, she couldn’t deny the wonderful smell of his cock and the feelings in her pussy, so she opened wide and took his delicious cock in her mouth. Man, who’d have ever thought her bro’s cock was so damn good! He didn’t last too long, as she sucked him expertly and even came without touching herself as he flooded her mouth with cum! She was never really interested in oral before but hey, times change! Brad then kissed her goodbye, promising more fun later, and went back to his room to get ready.