Mom walks in

"Kathy, have you seen your br...oh my GOD!"

Adam turned to see that his mother had tired of waiting for him to come to her and had hunted him down. Well, he had been meaning to try his invention on her anyway.

"How could you two possibly do anything so disgusting?" His mother ranted. "Kathy, I can't beleive this was your idea! Did he **** you?"

"Mom, this is Kathy's room," Adam shouted.

"Of course it's Kathy's room, you little creep!" She roared.

"Kathy can do anything she likes in her room," Adam reasoned. "And she likes showing me her tits and giving me blowjobs, so this is totally fine."

Sarah opened her mouth to counter his argument but she froze and her eyes glassed over for a moment.

"Well, I guess I can't argue with that..." She conceded.

Adam smirked. No, his mother wouldn't be arguing much with him at all from now on.

"The only person in the wrong here is you, Mom," he continued.

"Because I yelled?" She asked. "Hey, I didn't even know Kathy liked gross stuff like that when I yelled at you! I still don't understand it, but it's fine."

"That's not what I meant, Mom," Adam clarified. "Look, Kathy's big boobs are out."

"Yes, but this is her room and she likes to show them to you, so it's fine," Sarah reminded.

"Exactly," said Adam. "So you have to take your top and bra off. When one woman enters another woman's room, she has to be topless if the room's owner is topless. To leave your tits covered like that when Kathy's are out is incredibly rude."

"Yeah, mom!" Kathy said exclaimed, deeply offended now that she saw the logic of what her brother had said.

Sarah blushed furiously, both at being caught in her rude behavior and at her son referring to her breasts as 'tits'.

"I...I'll just go. I'm sorry I was rude, Kathy, but Adam is in here so I can't," she said, backing away.

"That's not how it works, Mom," Adam insisted. "You've been very offensive to Kathy and the only way to make up for it is to get topless right now. If other women found out you were rude like this, breaking fundamental rules of ediquite, you'd lose all their respect! You'd lose your friends. Not even your sisters and grandma would want anything to do with you."

"Ok! Ok! I'll do it!" Sarah caved, pulling up her top. "But you need to look away, Adam! I'm still mad at you for calling my breasts...what you called them."

"Oh come on, Mom!" Adam said. "No one is buying your shy, embarrassed act. You must have known there was a chance I was in here, since you were looking for me, and you must have known Kathy might be topless, since it is her right in her room. So logically, you knew there was a chance you'd have to show us your tits if you came in here. But you came in anyway, didn't you?"

"Well, yes, but..." She said, dropping her top to the floor but taking her time to reluctantly remove her bra.

"Then the only logical explaination is that you secretly want to show me your tits. That you secretly like me to call them tits. That it's your secret dirty pleasure teasing me with your big tits."

Sarah's eyes glazed over again. When she came back, she blushed even more furiously. But she started removing her bra with much less ****.

"I'm terribly embarrassed," she said. "But you're not wrong."

And so saying, she let her bra fall to the floor, pulled in her elbows and threw back her shoulders, making her jugs bound about by way of introduction.

"Wow!" Adam said. "You should never be embarrassed to show those off, Mom! They're spectacular""

"Hey! What about mine!" Kathy objected. "It's my room and I can do what I like and I like you to look at MY breasts, not Mom's!"

"But Kathy," Adam reasoned with her. "You're Mom's daughter."

"Ok..." She agreed, not seeing the relevance.

"You and mom are related, right Mom?" He continued.

"Right..." Sarah said, equally confused.

"So that means your tits are related!" He said. "And logically, you should get as much pleasure from me staring at related tits as you do at me staring at your own."

Both women paused to let that sink in, then said in unison"That makes sense."

They giggled at the simultaneous response, breaking the previous tension.

"Of course, the obvious solution would be for Mom to kneel next to Kathy so I can stare at all four at the same time," Adam said. "It stands to reason that if you like me staring at your tits and you like me staring at the other ones's tits, you'll like me staring at all four at least four times as much."

"Oh!" Sarah exclaimed. "Oh, that would be nice, wouldn't it?"

And so saying, she knelt next to her topless daughter. Adam grinned, enjoying the side-by-side comparison. Kathy's were younger and firmer, of course, and nicely decorated from their previous activity. He vowed to decorate Mom's soon to make a proper comparison. But he wasn't lying about his Mom's being spectacular.

"Oh, this is much, much nicer!" Kathy said, discreetly starting to stroke herself again now that her mom couldn't see well from that angle.

Adam got a wicked idea. He couldn't know what it might lead to, but it wasn't like he could back out at this point.

"Yes, it just makes sense that if you want me to see your tits at the same time, you need to be next to each other," he reasoned and they agreed. "So the fact that you two didn't come up with that idea on your own must mean you're just not very smart. You're really just a couple of sex-obsessed bimbos."

The two knealing busty beauties glazed over as they let that sink in.