Matt rang the doorbell to his house. He was still just in his swimming trunks.

His sister, Melissa, opened the door, and, while talking on her phone, accidentally bumped her face into Matt's pecs. Melissa quickly got off her phone, and then started admiring the muscular teen's torso, and then she smiled when she saw his cock pressing against his swimming trunks.

"Oh, I'm so sorry! Please come in. Are you one of Kyle's football teammates?" Melissa asked with a slightly seductive tone.

"Uhh... no. It's me, Matt." Matt said.

Melissa turned around and looked at Matt's face, and realized that it was indeed her younger brother's face. Melissa's smile and happy attitude promptly vanished, and started to be filled with fear.

"M-m-matt? What happened to you? You must be bigger than Kyle!" asked Melissa.

"I don't really know... I guess I just had a growth spurt while at the pool." Matt responded.

Melissa just looked dumbfounded, and then walked into her room and closed the door. After that, Matt's mom came in, and Matt quickly explained the situation.

"Well, I guess we'll need to take you to a doctor tomorrow..." Matt's mom commented.

"Can I get some new clothes?" Matt asked.

"I won't be able to get you anything until after school tomorrow. Maybe you could ask Kyle?"

Matt nodded and headed up to his brother's room. He knocked on the door, but Kyle didn't respond. Matt knocked lightly again, since he didn't want to accidentally knock Kyle's door down. Again, no response. Matt decided to just give up, so he went to his room, closed the door, and tried to get out of his swimming trunks.

Unfortunately, his swimming trunks were too tight for him to take off normally, so he just ripped them off. Matt was aroused at how easily he did that, and quickly got an erection that was easily over nine inches long. Just at that moment, Melissa opened the door, wanting to see whether her brother really was huge now, or if it was a dream. Too late, Melissa realized what she was seeing, and her jaw dropped at Matt's huge cock. Melissa was dumbfounded that her 15 year old little brother had a cock bigger than any boy she'd ever seen. Melissa then left the room, speechless, and didn't bother to close the door.

Matt went over and closed the door, and, after his cock went flaccid again, put on a pair of boxers. He was barely able to get it on, and of course, considering how tight it was, his manhood was easily visible. Deciding that the most he could manage to put on would be his boxers, Matt went to bed.

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When Katie got home, her mother was equally surprised, and, like Matt, Katie would go to the doctor and get new clothes tomorrow. Katie went to her room, and changed out of her bikini, but seeing that her bras really didn't fit, Katie went to her sister's room, and opened the door while topless.

"Hey, Julie! Can I borrow one of your bras? Mine don't really fit anymore." Katie asked.

"Well, maybe you shouldn't eat so-" Julie started, but when she saw her sister, she was shocked.

"Oh my goodness, Katie! What happened to you?" Julie said.

"I really don't know. I was swimming at the pool, and all of a sudden, bam! I grew! And something similar happened to my boyfriend..." Katie said.

Julie looked at Katie's large rack, and then felt her sister's boobs in her hands.

"Wow, they're so big and heavy! I think you're quite bigger than me! I don't know if my bra will fit, but you can try." Julie said.

Katie nodded, and then grabbed one of her sister's C-Cup bras. It barely fit, but it looked like it was going to snap at any moment. Katie then went back to her room.

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Back at Connor Venten's labs...

"Mr. Venten! The two have left the pool." said an assistant.

"Hmm. And how did the chemical do?" asked Mr. Venten.

"They've grown quite a bit above average." commented the assistant.

"Great. Now, what can we ask the boy that makes us sure he wants to be bigger?"

"Maybe we could ask him if he'd like to be big enough to win the Mr. Olympia contest."

"Great idea! And once he grows some more, we need to make sure that the Mr. Olympia contest actually comes here so we know that he is big enough."

"Yes, sir."

"And what about the girl?"

"Maybe she'd like to be the captain of the cheerleading team?"

"Yes, yes, great idea. Let's hope they come to the pool tomorrow. Oh, and make sure that cheerleading tryouts happen soon."

"Yes, sir."

And with that, the assistant left, leaving Mr. Venten to himself.