His sister's changing before his eyes

Parker's eyes lazily fell upon his sister's, as a sudden inexplicable attraction towards her washed over him. He never noticed how hot she was. Before he could help himself, sudden perverted fantasies filled his mind. How she would look naked, how she could squeal if he stuck his...

'No! Stop it!' he said to himself, shaking his head, momentarily getting the image out of his brain.

"Parker, what's gotten into you?"

He looked back at her. For a moment, the perverted fantasies had come back. He wondered what she would look like with E-cup jugs. He imagined her modest bust swelling... popping open her blouse and...

And then, he realized it wasn't a fantasy. Her breasts were indeed growing, straining her bra as the front buttons of her outfit popped open, showcasing her developing cleavage, all while she was blissfully unaware.

He couldn't do anything but stare, his mouth fallen open. His mind was frozen behind feelings of confusion, disbelief, and growing lust. He didn't even try to hide his ogling, as he stared right down her cleavage.

"P-parker... what..." Rachel began, before noticing a strange weight on her chest. Looking down, she froze. A moment later, she screamed.

"What the hell?! What's happening?!"

She grabbed her still growing jugs in her hands, before letting out an involuntary moan, as she found them far more sensitive than she had anticipated. To top it off, she still wasn't done developing as her bra finally broke. The **** of her melons being released was enough to break the final button, as her new mamaries spilled out, bare to the world.

"This can't be happening! This... this can't be real... I... Parker help me!" she cried, looking up terrified at his brother. However, the face he was giving her was far from comforting. His tongue was hanging out, drooling. His eyes were locked onto her nipples, and his pants were tented beyond belief.

"T...t...ti... titties... sooo...." he moaned, as he took a step towards her.

"Parker! PARKER! Can you hear me! I need you! Please stop looking at me like that! Help me!" she yelled in mounting fear, while her breasts grew another full cup size.

"R-rachel... I... I..." he stammered, a small spark of resistance still in him... trying with all its might to resist his every temptation to throw his sister to the ground and fuck her raw... a resistance that was rapidly getting drowned out.