He owes his sister a return favor

While their mom wiped Matt's cum from her face and tits, Matt turned to his sister. "I owe you, Karen, so get ready."

"Huh?"

"You can't do your sister," their mother protested. "Think of her future if she got pregnant."

"I'm going to go on birth control," Karen said. "But yeah, until then, it's not a good idea."

"This isn't one of those porno things where the guy has a pregnancy fetish," Matt said. "Actually, I had another idea. He rolled Karen on her back, put his face between her legs, and went to work.

She was turned on already--he could tell that from the liquid puddling from her pussy as well as from the blush that extended from her face all the way to her twat. Still, he remembered her lessons, approaching the target deliberately, teasingly. He kissed her inner thighs and ran his fingers over her belly, then stroked the outside of her outer lips before lightly kissing them.

She shuddered at his touch, then moaned when he kissed her.

Matt heard a squishy noise and took a break to look at his mother who had her fingers in her twat and was masturbating as hard as she could.

"No," he told her. "You don't get to relieve your own pressure. If you need to cum, you can ask me or Karen. If we give you permission, fine. Otherwise, hold it."

"But--"

"No buts," he concluded before getting back to work.

Karen giggled.

But she wasn't laughing for long as he slid a finger into her pussy and started circling her clit with his tongue.

It was still too early to pull back the hood and apply direct pressure but that time was coming... and Karen was bucking against his touch, trying to get more. So, he gave her a second finger.

Her pussy muscles clamped down on it like a muscleman's handshake.

Now, he thought. He tongued her clit and she exploded into orgasm, bucking against both his tongue and fingers, pressing herself against him, making little squealing noises while her pussy dripped with moisture.

"Shit, Matt. I've created a monster. Do you know how much better you are at that than the last time."

Their mother opened her mouth, then buried her face in her hands. "Last time," she muttered.

"Hold me," Karen said. "Mom, you should go down to the foot of the bed and sleep across our feet. Until you're ready for Matt to fill your cunt with his semen, you don't get to sleep with the sexually active."

"Is that what you want, Matt?" his mother asked.

"I think Karen is right. The bed is for the adults. Until you're willing to participate in adult activities like fucking, you can sleep at the foot."

"Yes... master."