Almost but not quite

Matt released his load into his sister's mouth. He'd thought Cindi had drained him but it was as if she'd just built up the pressure. It felt as if he kept pumping for minutes.

At first, Karen kept up, gulping down large mouthfuls as he squirted them out, but before long, she lost her breath and came up for air... while letting his cum continue to shoot over her cute face.

"That," she said when his semen flow slowed a little, "was really nasty stuff."

"Keep pumping with your hands," Matt said. "There's more."

Karen sighed. "I guess I'd better try sucking it down. No point in asking for a lesson if you don't want to learn it."

"Good idea." He guided her mouth back over his dick and, as she pumped hard with her hands, managed a few more massive shots into her mouth.

A minute later, she swallowed the last of it. "Totally intense," she said. "I mean, like, I've seen videos, of course. But they're gross. Like, guys forcing the girls when they don't want it or when they're obviously pretending that they're almost coming just from sucking dick. It's sexy, don't get me wrong, but it's not orgasmic or anything."

Matt had enough sense not to tell her it was plenty orgasmic to him. "It felt really good. I think whoever gets you as a girlfriend is going to be really lucky."

"I'll need to be better by then," Karen said. "I wanted to swallow all of your load and I couldn't."

"Hey, this was your first try. You did great."

"You're the best brother."

Yeah, right. He was a complete perv who'd just unloaded about a gallon of cum into his sister's mouth and showered her face with more of it.

"Now," he said. "We had a deal. I help you, you help me. I want to return the favor but you've got to tell me what feels good and what doesn't."

"Are you sure you really want to? You don't have to, you know."

"I'm sure."

She sighed. "But if it grosses you out, promise you'll stop."

"Yeah, sure."