The group hopped into the family minivan, buckling up for the short trip. Melanie and Robby sat quaintly together in the back seat while Lilly, their mother, took hold of the steering wheel.

Driving to the birthday party turned out to be more than just an idle process for Rob. He found himself eyeing his mother's more prominent frame. Her breasts stood big and firm against her chest as she drove, jiggling in the slightest when making turns, quietly hinting to him that their soft texture still remained despite their increased size and mass.

Rob knew it was weird to look at his mother in that way, but he was a man, and a man has a right to admire the female form-- regardless of who it belonged to! And with that reassurance, Rob took it as all the more reason to continue leering!

It wasn't just her motherly tits that had swelled, but other parts of her frame had become more defined as well. Her baby-carrying hips had grown, widening further as they portrayed her gender in the most sultry way possible. He could tell by how they stuck out more in the car seat. Boy was it a sight to see.

Immediately as the thought crossed his mind, Rob felt himself getting too carried away with his daydreaming once again, feeling his member begin to harden inside his pants.

It seemed like some devious plan from the heavens because at that very exact moment, Lilly looked into her rear-view mirror to check up on the two of them. Rob swatted his hands towards his crotch at the sight of his mother's eyes through the mirror, attempting to cover his burgeoning bulge.

Lack of a good memory, Rob neglected to remember his sister sitting right next to him. Melanie was blinking at him with her big blue eyes, confused. First she looked at his face, then down at his hands, and then back up, wondering what the hell was going on.

She wanted to speak, but she held her voice of back, sighing in the process. It was best left unspoken.

Rob saw no part in her withdrawal and continued to try to play it all off as one big misunderstanding to everyone around him, readjusting his legs and his seating position.

"What?" Rob snapped, throwing his hands up in the air at his sister.

"We're almost there! About 5 more minutes!" Rob's mom announced.

"Yay!!!" Melanie cheered, wrapping her arm around her brother.

"yay..." Rob echoed unenthusiastically. He still couldn't believe he agreed to go to this thing.

Rob peered out the car window just as they reached their destination. There laid a house that one could almost classify as a mansion, yet not quite so luxurious. It was however immense, with large trees surrounding the property, providing shade even on the hottest of days.

"We're here we're here we're here!" Melanie exclaimed, fidgeting wildly in her seat as her mother parked the car.

The long cobblestone pathway presented Rob with a movie-like sensation. Each stone was placed ever so meticulously, as a way to welcome the many guests that would be walking on it this morning. The splashing sounds of giggling young girls escaped from the lofty Spanish-style house, letting the Robinson family know what lie ahead of them. Melanie's smile grew only wider.

An archway through the center of the house embraced the newcomers as it guided them towards the backyard.

Lilly caught sight of the other mothers mingling about as Melly saw her friends splashing about in the Olympic sized pool. The hostess, obviously the mother of the birthday girl came up to greet them.

"Why hello there!" She greeted Lilly politely, shaking her hand in the process. "You must be Melanie's mother. You've grown such a fine young woman, you know that?"

"Why thank you," Lilly spread a white smile towards her new friend, "Ashley's quite the well-mannered lady herself."

Rob and Melly peered out across the vast backyard only to quickly be interrupted by Ashley's mother.

"Why don't you two go put on your swim suits! The bathroom is up the stairs to your left!" Her voice faked excitement and energy.

Without so much as a response, both of the Robinson's kids ran inside the house.

"I had no idea Ashley was so...rich." Rob blatantly said, standing in the huge marble bathroom.

Melly payed no mind to her big brother's comment, and proceeded to take her clothes off.

"M-mell, what are you doing?!"

Melanie stopped dead in her tracks. "What? I'm changing to go swimming. We're family, there's nothing to be ashamed of." , continuing on with taking her shirt completely off.

Rob stood mute, staring at his sister's naked torso. It was so wrong, but he couldn't help but feel curious about the female body. Her pert breasts stuck right out in front of her chest and reminded Robby of the few times he had seen her training bras in the laundry. At the time they could only barely fill those, but now thanks to her recent growth spurt it appeared as though she could almost out fill an A-cup. Rob's gaze shifted downwards as she began to slip her jeans off, revealing her bare privates. It was the first time Rob had seen anything like it. He stared.

Melanie payed no mind to it, casually slipping her bikini on.

"You gonna change too?" She finally inquired, realizing he still hadn't stopped staring.

Rob flinched at the realization and instinctively started to take his clothes off.

He positioned himself very carefully, hunching forward as he stripped naked in front of Melanie. The last thing he wanted to do was have his sister see his rod, but it proved to be nearly impossible when in such close proximity with her. Rob quickly slipped his jeans off only to already catch Melanie staring directly at his crotch. Her expression is what got him. She appeared extremely fascinated, being the first time she had ever seen a penis before. She stared and stared, admiring his length as Rob fumbled to get his swimming trunks on. How embarrassing!

Melanie smiled once she found Rob staring back at her. Unlike her brother, she couldn't care less if she was caught staring or not, and proceeding to walk out of the bathroom.

Rob desperately tried to have a word with Melanie about what had just happened, but it was too late, she had already frolicked off. He found himself at the pool before he knew it, watching Melanie dive right into the pool after her friends. Rob took it as a hint to relax and take his mind off things. A particular lounge chair caught his attention.

After applying some sunblock onto his chest and shoulders, he found his eyelids quickly growing heavy as his muscles relaxed for the first time in two days. His mind wandered, traveling from one point to another, only to return to the same image of his sister standing naked before him like he had seen just moments ago. It was clear, as if he was still gazing at her idle form in the bathroom. His unconscious, sleeping mind took hold of what he saw, bringing forth his most primal instincts-- regardless of its target.

First, he dreamt that she started stretching in all kinds of outrageous ways, spreading her long legs as far apart as possible. Her arms were next, being tucked behind her back as a means to thrust her tiny breasts as far towards her big brother as she could. He felt his face flush from the embarrassment and shock, but his dreaming mind continued the painful barrage nonetheless.

She began talking dirty to him, though now she was no longer his sister, but a very sexy classmate he admired who looked strikingly similar to his baby sister-- almost identical.

"Mmmm...." moans escaped from the girl's subtle lips. "Ohhh...Uhhhhhhhhhh!!" her voice echoed in his ears so strikingly similar to that of his sister's. Waves of pleasure coursed through his veins with each passing heartbeat as the sun shone down upon his physical form, outside the dream world.

"Oh god.....Robby." her lips muttered. "…..Robby..." He felt his trunks lift at the crotch.

Finally, he imagined what he dreaded most: his little sister—or this woman—was growing...maturing....becoming all the more womanly. At first he only added two inches to her frame, but soon he found himself lengthening her shoulders and swelling her breasts to what looked like two average sized grapefruits. "There we go", his sun-baked face grinned mischievously.

Just then he sensed the light on his face vanish. He opened his eyes to greet a close-up of Melanie's face.

"Do you mind?" she held up a bottle of suntan lotion.

"No no, of course not." Rob responded automatically, leaning up from his delightful nap.

It was when she twirled her body away from him that Rob noticed she had changed yet again, and it wasn't just coincidence! She had morphed into exactly how Rob envisioned her! Rob took a deep breath, realizing exactly what he'd just done unconsciously. He surveyed her body, trying to scrape up some sense of shame and guilt for what he had done, but the allure of the opposite sex was still there. His sister had changed yet again, and in his unconscious mind...for the better. In his conscious mind...for the better.

She sat down at the tail-end of the lounge chair, moving her long hair away from her back. "Do my back first please." She politely asked, pulling at the string of her bikini top. She used both hands to cup her modest breasts inside her bikini top whilst Rob had her full bare back to work on.

Rob squirted some lotion onto his hands and hesitantly began to massage into her warm shoulders and arms. "Mmmmm....that feels SO good."

The soft, squishy sensation of her meat as he lathered her arms sent shivers up Rob's spine. It was like nothing he had felt before. Never in his life had he felt something so soft and sensuous. His mind slowly began to drift unconsciously back to the vision of his baby sister.

There she was, both in his mind and in front of him, growing, he imagined. It was as if he had control of the situation, because within moments he felt his hands slowly slip further down her back, but he did not move his hands.

"Ooohh..." She cooed, as Robby's hands expertly spread the slippery substance all throughout her lower back and waist.

He increased her height more as he closed his eyes, finally making her the same height as Rob. He felt his fingers slip with the lotion slightly apart as her torso grew wider beneath his touch.

"Now my stomach." she insisted, completely unaware of her transformation.. Rob silently obeyed, moving his hands around her after adding more lotion.

This time he added four more inches to her frame. Instantly, he felt an explosion of female flesh hit him as her body surged larger and larger against him now, pushing one of his legs completely off the lounge chair. She unconsciously cleared her throat, "Hnnhnnn!" It made Rob flinch out of fear, but only to quickly remember her lack of awareness to the situation at hand.

Rob knew she couldn't sense him changing her, but still he felt the need to be silent.

Yet still, he continued. And with the rhythm of the motions of his hands on her stomach, he envisioned her breasts swelling larger. At first only a cup in size, but then a few more. Immediately he felt her posture alter as the added weight caused her posture to suddenly slouch lower. The back of Rob's hands grazed the very undersides of her new swells as they became harder and harder to ignore.

Rob found himself compelled to slowly move his hands closer and closer to the goal in mind, only stopping to gauge her emotions as he tested the water. Just then a mischievous plan came to mind.

Rob made her grow another cup size larger, causing the increased weight of her breasts to slightly teardrop more, covering his fingers in the process. Rob couldn't help it, extreme jolts of pleasure shot through his veins at that very moment, hardening his cock in his pants all the more. His neck was on fire... and Melanie could sense it.

Now with a sense of uneasiness filling the air, Rob took extra care with each step he took. Slowly, with the mindset of a child not wanting to wake up his parents, he continued to gyrate his hands over her ribcage all the while her womanly flesh pressed against his knuckles. Nothing could beat that moment, except for when Melanie reached over to pull one of Rob's legs on the other side of her, allowing room for her to scoot even closer to his stone-skin crotch. He somehow managed to harden further.

At that moment his sense of reality had dwindle to nothing, his mind being plagued with wave after wave of sexual encounters that he could(literally) only dream of. His mind ran rampant.

So he continued his sex-crazed assault on Melanie's body, making adjustments to her ever-improving form. First he imagined tiny freckles sprinkling over her cheeks and nose. Then he envisioned her eyes. They were no longer the big baby blue eyes he could picture so clearly, they were green now and sparkling like emeralds. They felt oh so warm and welcoming, and only helped to accentuate her developing goddess of a body.

He opened his eyes and met them in person for the first time. They burned on a very humble note, scarring his soul as he stared deeply into his sister's eyes. It was then that he realized...he was creating...someone else!

But that did not stop him. He continued, altering her hair to what one could only describe as the most vibrant colors of a maple tree. Strands of her hair shone bright red and orange on the pool's reflections. Without saying it, this only strengthened the allure her eyes presented to the new her.

"I think you've massaged there enough! You're beginning to give me a rash." She giggled, "Why don't you try up here?" She grabbed Rob by the hands and placed them over the softest material known to man: her boobs, her breasts, her ta-tas!

The sound of a girl in sandals walked in to interrupt Rob in the most ecstatic moment in his life. Nooo!!!

"Melanie, what on Earth are you doing!?" The unknown voice called out. His goliath of a sister was blocking everything in front of him.

"Oh nothing, Rob's just helping me put on some suntan lotion. Isn't that right hun?" She turned, staring directly into his gaze with her emeralds.

Rob cowered away, quickly overcome by the beauty of what he had just created, and stuck his face against his big sister's back.

"Awww...he's so shy isn't he?" The unknown girl spoke.

"Yea, he can get that way."

Rob felt his arms wrap tightly around his sister as he kept his eyes shut. A sense of safety overcame him...and it turned him on beyond belief. Her warm skin felt good against his cheek. In response his trunks began to push up against his sister's lower back. Soon his entire length lay resting against her and there was nothing he could do about it! So he clung onto her for deal life...helpless.

Wave after wave of pleasure hit him as he began to rub against her quietly. He couldn't help it, it was too much. He just couldn't help but envision her body growing again-- but no! Rob tried with all his might to focus on other things! Anything... but.... her!!! It was impossible. He visualized her body growing right in front of him!

Quickly he felt the sister he wrapped ever so tightly around begin to push his embrace away. He opened his eyes and saw as she began to take up more and more of the lounge chair, leaving very little room for him!

The two girls continued to mingle, unfazed as the growth continued.

It didn't take long for Rob to realize that Melanie was no longer wearing anything to cover her great big breast! He could only make out their presence from behind her by taking small glances under he arm.

"Shhh shhh, it's ok Robby." he heard his sister comfort him.

Rob readjusted himself with legs spread painfully apart and latched passionately against his sister. This proved to be a meaningless task as he was the cause of this colossus girl to become so large, yet he still attempted to find shelter against her for all that he was worth. This was all too much! He tightened his grip, quickly realizing one of his hands had landed directly onto one of her tits! But instead of a negative reaction, Rob found her looking down at him... almost maternally.

"Why don't you come say hello, Robby?" She turned her huge body towards him and grabbed onto his little waist, hoisting him up in the air and onto her lap. The other girl laughed as Robby's eyes first settled on her. He gasped it shock as he realized the girl standing in before him was none other than Katie, one of Denise's friends!

She too had nothing covering her huge breasts from plain sight as they hung ever so perfectly off her youthful body. And her tanned skin echoed sexuality, which only ripened those wonderful melons of hers. He couldn't help but lick his lips at the sight of her plump, lively nipples.

Upon further inspection, the finest of golden hairs could be seen scattered across her chest, no longer than an eighth of an inch in height, but shining from her freshly dried skin nonetheless. In a strange ambient way, they seemed to accentuate the beauty her young skin had on her big bosom.

"How's it going Robster?" She chirped, throwing Rob out of his daydream while leaning forward to ruffle his hair. Rob could only eye her tits as they lifted off her chest to hang ever so enticingly next to his face.

Rob simply nodded in response. His voice was long but gone after rendering his 'baby' sister into a tall sex goddess. It was al SO SO wrong.

He watched as her attention quickly left him and focused back up to Melanie.

"So how long have you two been going out?"

…

…

…...................

Melanie was casually resting her hands on Rob's shoulders as she spoke, "Oh I dunno...about 7 months now? Right Robby?" She leaned over him to meet with his eyes.

"I-I-I"