Katie couldn't pinpoint the exact time she figured out she wanted her brother. It started off as a subtle urge, an itch she couldn't scratch no matter how much sex she had. All she knew was that she needed her little brother inside her.
Matt had always been cute, with his piecing blue eyes and blonde hair. But as he had gotten older his baby face had lessened, his cheekbones grew more chiseled, as well as his body. Every time Katie caught a glimpse of him shirtless she pictured herself licking her way down his abs, lower and lower. He was tall too, 6'1, and built. Katie had never seen his cock, though she wished she had, but his bulge straining against his sweatpants was enough for her to know that her little brother wasn't really all that little. Now that he was 18 he was really a man, she wondered how much sex he had had, if any. He had never had a girlfriend.
Katie herself was conventionally beautiful, long tan legs and a firm round ass. Her tits were her best feature, supporting a 32DDD, they seemed a little too big for her slim little body. Often her thoughts wandered, thinking of her little brother sucking and licking and nibbling on her nipples. She had taken to not wearing a bra around the house, claiming it was more comfortable. In reality she wanted Matt to see her nipples through her too tight tops. She spent a lot of time teasing him, wearing shorts that rode up her ass and hugged her pussy. Katie would leave the bathroom door open and strip slowly, hoping he was watching her. As soon as she made it into the shower her fingers would immediately be rubbing her clit, another hand pulling at her nipples. Long blonde hair soaking wet and falling down to her waist. Beads of water dripping along her body, down to her always clean shaven puss.
It was the very next day when Katie was wearing another one of her too tight outfits. Today is was a purple top and grey booty shorts. Her mother was complaining about it again over breakfast.
"I just don't understand why you feel the need to walk around like that sweetheart," her mother chided.
"I think its comfortable," Katie said, "what do you think Matt?" His eyes flickered to her face for the first time all breakfast, a flush creeping up his neck and cheeks. Katie licked along the edge of her spoon whilst gazing into his eyes. She wished her tongue was running up his cock instead.
"I think she looks fine mom," Matt said smoothly, swallowing slowly. Katie pictured him grabbing her and fucking her in front of her prude mother on the kitchen table. Pumping her full of his cum whilst her parents watched. Her pussy ached and she rubbed herself discreetly along the edge of her chair. Her brother was definitely staring at her chest now, her nipples stretching the thin material of the shirt.
"I think that she should change," her mother argued.
"Fine," Katie huffed out, she shimmied out of the kitchen, making sure that Matt got a good glimpse of her ass as she did so. She yanked off her top when she got to her room, and went poking around in her dresser for a bra. A knock sounded on her door, she assumed it was her mother coming to scold her.
"Come in," she said sweetly. But it was Matt, even better.
"Oh my god," he said staring at her. She had forgotten that she wasn't wearing anything on top. Her breasts were in full view, nipples hard little nubs, begging to be sucked on. Matt covered his eyes quickly.
"What's wrong little brother?" Katie asked inquisitively, "never seen boobs before?"
"Mom says you can come down when you're wearing something more appropriate," Matt said, "and if we are on the topic, no I haven't."
Her little brother had never seen breasts. He really was innocent despite his looks.
"Well," she said, "why don't you look?"
"I shouldn't," he mumbled, hands still over his eyes, "its not right K,"
"It can be our little secret," she said sweetly. She walked over to him and removed his hands from his eyes, placing them down on her boobs. His entire face was red.
"Now move your hands around," she breathed out. His hands moved of their own accord, pulling and massaging her breasts his fingers gently brushing her nipples. He glanced down and then couldn't seem to tear his eyes away.
"Do you like them little brother?" She asked, god her panties were soaking wet. She needed him.
"I do," he said, swallowing again.
"I can tell," she responded, running her hand downwards, palming the bulge growing in his pants.
"You've never been with a girl have you?" Katie voiced her thoughts.
"No, I don't know anything about it too," he said, annoyed all of a sudden. He removed his hands from her. She moaned softly in protest.
"Well, I could always teach you?" She murmured, going back to stroking the outline of his cock through his pants.
"No," he said breathily through a soft moan, "K, its wrong,"
"Come on Matty," she cooed, "I'm your big sister, its my job to teach you things," he thrusted involuntarily into her hand and let out another moan.
"Come to my room tonight, I'm sure you'll make a great student," she said.
It was 12am now and Katie wasn't sure if Matt was going to come, but she lay on her blankets completely naked, trying hard not to touch herself. It had been so hard all day, the two of them stealing glances whenever they could. She could picture his hands on her breasts again, and placed her own there slowly massaging them, her breathing becoming heavier.
"You're already starting without me?" Matt said from the doorway. Katie's eyes sprung open but she didn't stop.
"I was thinking of how it felt this morning," she said noting her brother was only wearing his boxers, "want to remember too?" He hurried to her bed, shutting the door and climbing up onto her bed, hands immediately on her breasts again. Katie immediately moaned loudly, rolling her hips upward.
"K, this is so bad," he mumbled.
"Don't stop," she whined.
"You promised you would teach me," Matt said.
"Of course little brother," she said. "You're already doing a good job. What do you think comes next?" Matt looked at her breasts.
