"Cat!" Kit yelled from across the road upon seeing his sister. Cat turned around on the sidewalk, and waved back upon seeing her brother. They had both just returned from school at the same time, it seemed. Kit quickly checked both ways, before crossing the cul-de-sac.
"Mom and dad aren't home yet, wanna' play?"
Cat blushed slightly, the memories of another intimate and sweaty weekend still weighing heavy on her mind, but was none the less as excited as her brother.
"I still have homework, but I can do that after they're home." She tried to hide her excitement, but her lower half was already tingling in anticipation. They walk to the front door together, but Kit's the first to get out his key and open it. They quickly got rid of their jackets and backpacks together, but as Kit scooted off to his room to prepare the condoms, Cat headed to the kitchen. After the first time they almost got found out, they learned to take precautions. Cat checked the time as she picked up a timer, and quickly dialed in 45 minutes. Their parents wouldn't be home for another hour or two, but they needed time to clean up, get dressed, heck, sometimes even shower. Fox semen, or presumably any semen, didn't exactly wipe easily off of fur. With a loud beep, Cat started the timer, and placed it on the nightstand in Kit's room. Kit, of course, was already down to his briefs, his pants hitting the wall as Cat had entered the room.
"Let's lick each other." Cat said confidently, tossing off her shirt towards Kit's pants. As she crawled onto the bed, Kit pulled her down, and following a giggling wrestling session, all the remaining clothes were scattered across the room. Kit had won, and was on top, but Cat didn't want that. "Can I be on top?" Kit nodded, and rolled off of her, patiently waiting with his red, massive member standing at full attention. Cat cautiously planted her derrier atop her brother's face, before gently putting her weight on him, as she leant forwards. She hadn't even grasped his cock before Kit's tongue was fully occupied exploring her depths, and his fists firmly grabbing her rear. Slurping and sucking filled the room, and it didn't take long until moaning joined the choir. Despite how much they had been going at it ever since Twilight had encouraged them to practice, they were still learning where each other's sweetspots were. Didn't help that they never talked about what felt good for them, except for when it was exceptionally good. Cat lifted her head off his cock.
"I don't want to clean my fur today, can you give me a condom?" Kit pulled his wet, messy face away from her rear, and started handing her a condom, but stopped before it was in her reach. "Only if I can put it in you." Cat lips formed a mischievous smile, as her gaze met her brother's. "Only if you'll lick me in the bath." Kit was always quick to overpower her in the shower, and while she always had fun sucking his dick, she felt that he didn't return the favour enough. Kit stopped for a moment, before declaring "Deal!" and handing over the condom. Cat had become a master at applying condoms, and could do so blindfolded. Before she could mount him, however, Kit pushed her down on the bed again, planting himself between her legs, and started making his way inside of her. Cat had learned the value of lubrication after a time where they tried sex without any foreplay, after which she quickly concluded 'never again', and thus, her juice and saliva soaked pussy easily took him inside.
Without a second thought, Kit started fucking her tight hole with full force, slaps and slimy sounds joining with their combined moans to form the soundtrack of their play-session. With every thrust, the two cubs bounced upon the bedsprings, and what little resistance Kit could muster quickly dissipated. He stopped briefly, preparing one final thrust, pushing his (comparatively) massive knot inside of his sister. As her already tight hole gets stretched to its limit, Cat is overwhelmed. She clutched herself around her brother, toes curled, claws digging into his fur, crying out from equal parts discomfort and pleasure. And yet, the instant she felt her brother's cock throbbing inside of her, she stopped, all the pain gone. She got lost in his eyes, as a feeling of pure joy washed over her body, enveloping her like a silken sheet. Every single muscle lost all strength, as she collapsed right in front of her brother. Moments later, Kit collapsed on top of her. Their heaving chests pushed against each other, as they both tried to recover from the ordeal.
"Cat, are you okay?" Kit sounded genuinely concerned. He had never seen his sister collapse like this before, but he had also never knotted her before. With how his own orgasm had felt, he could only imagine what it must've been like for his sister to almost pass out. Cat spent a few seconds processing what he said, before she finally nodded twice.
"I'm sorry I didn't warn you, I-" Cat cut him off, something she hadn't done for years, by pushing her finger against his lips. Feeling her strength returning, she turned her head to face him.
"That... Was the best."
Cat wasn't sure what compelled her to do it, but she put her arms around his neck, and pressed her muzzle against his, kissing him deeply. Breaking the kiss, she continues speaking.
"I... I think that's enough for today. I'm tired."
"Me too."
Kit finally pulled his now somewhat smaller know out of his sister, revealing the tennis ball of semen he had unleashed inside the condom. Although they didn't say a word while cleaning, neither of them could stop smiling. As Cat turned on the shower, Kit finally had to ask.
"So what about our deal?"
Cat looked at her brother for a moment, before she realized what he meant.
"Actually, I'd rather just we... Hug, for a while."