Mark and Kate's Dozen Rules

"I thought you were out with Emma," Kate said.

"She's spending the day with her friend Jill," he said.

"So that we can have a romantic Valentine's Day?" she asked.

He shook his head. "I told Jill's parents you just needed a rest day." He slipped back into the sheets with her.

"I don't know if this counts as resting," she muttered, as he loomed over her, kissing her neck, his intent clear, and most welcome.

She took his face in her hands, kissing his lips as she hooked a heel around his thigh, pulling him into position on top of her.

"There'll be time for that too," he replied. "Probably."

His erection slid along her slit. Even though they'd gone further, many times now, it was fun to revisit this marginally more chaste stage of their courtship. They held each other tenderly as they settled into a rhythm, a constant push and pull between his lust and hers, between their desire and their willpower.

He clearly had more on his mind, since every so often, the tip of his cock would glance off her hole, the head inching in just far enough to give her a forbidden thrill before responsibly withdrawing.

She wondered if he was waiting for her to lose control, to give in. Part of herself grew excited at the possibility, of letting him ravish her, letting him claim her and knock her up. But if he couldn't be he clear-headed one, she would have to be. She had a handle on her fantasies, but just barely, and that grasp might slip if he kept teasing her like this.

"You're going to need a condom for that," she gasped.

"Oh? For this?" he teased, pulling away from her momentarily, his kisses trailing down between her breasts and across her belly, to the inside of her thighs, and finally to the destination between them. She moaned when she felt his finger inside her, touching her just right, even if it wasn't quite what she longed for most.

"No fair. Get up here where I can reciprocate," she said, feeling too weak in the knees to get up.

He got up on the bed, lying the opposite direction, his legs splayed, as his face returned to her crotch, his tongue dancing delicately around her sensitive clit. She took his erection in her hands, taking it into her mouth, sucking in all that she could of it.

She moaned around him, her arousal already building up, like a high, teetering tower. She redoubled her efforts, taking more of him little by little, feeling his hips push cooperatively towards her, but still considerately cautious and restrained. He wasn't fucking her face but he was moving to her rhythm. The enormity of his orgasm snuck up on him, as it sometimes did when she was involved.

He pulled his face away from lapping at her, just long enough to gasp, "Kate, I'm going to..." With her free hand, she pressed his face back down into her cleft, too close to let him stop or let up now.

With him still in her mouth, her orgasm crested. It was all she could do, to get enough air into her lungs while sliding her tongue around the sensitive rim of his head. Then she felt it engorge, in her hand and in her mouth, flooding her palate with salty fluid. Her whole body shook, and she swallowed it all in a gulp without thinking, even as more came flooding in a heartbeat later. When they were both sated and spent, they lay on their backs panting.

"No exchange of bodily fluids, huh?" Mark teased.

"Oh well," she replied, still breathless. "That's not the kind that matters anyway."

"I'm not complaining."

"Happy Valentine's Day to you too."

"I love you, Kate," he said.

She didn't want to give him the stock answer, the easy answer. She also didn't want to lie to him. So she took a moment to consider.

She knew they shouldn't be falling in love with each other, but that wasn't stopping it from happening. And she knew she really was falling for him. Before he moved back home she had been ready to entirely write off love, to write off relationships, and yet she'd found it all again, in the least likely place. It was actually a relief to know she wasn't the only one falling, even if that also meant that neither of them really had control over this anymore.

"I love you too," she said.

"Not like a brother. I mean, I do still love you as a brother, but...also much more than that now," he said.

"I knew what you meant," she teased. In the silence that she knew he needed filled, she added, "Me too."

"So what was it I need a condom for?" he asked, sitting up and getting one out of the box. He was somehow already firming up again.

"Good god, young man!" she laughed, as she pulled him back into her arms. "What are the townsfolk going to think, if you keep stopping in for condoms all the time?"

"Don't worry, I may have hinted to the cashier that I frequent the truck stop glory hole," he said.

--------------

"So our...uh...anniversary...whatever...weekend is coming up," Mark mentioned at the breakfast table. "Have you decided what you want to do with it?"

It had been his idea to mark the occasion somehow, but given that they were brother and sister, and the messy string of events that brought them together, it wasn't like they had a first date to count back to. So they started counting at the date when he had first walked in on her fingering herself. The day he had jacked off in front of her.

Sure, there were lots of dates when they reached other milestones and crossed other boundaries, but in retrospect, that was the day when they'd stopped being normal, innocent siblings. Although Mark that for him it had started before that. It had taken a while to build up the courage--or the insane level of horniness--to take that first step. By now he knew now that Kate had also started thinking about him differently before that.

Mark had a coworker with a daughter roughly Emma's age, so Emma was going to stay with them for the weekend. The official story was that Mark was headed out of town for the weekend, and that Kate had other plans with some guy.

Kate smirked, casting a pointed glance at where her daughter sat in a high-chair, half-eating half-playing with her cereal. It wasn't as if Emma truly comprehended what was going on between them, but it was probably still a good idea to avoid mentioning anything sexually explicit around her. If there was one way they could still get caught, it would be from a little girl who didn't know what to say to other people and what not to.

"I reserved a place up north, on the lake," Kate said. Mark was about to question sparing the expense, but she preempted him. "We've been saving up for so long. We've been on our best behavior this whole time."

"Oh, have we?" Mark joked.

For Mark, the rest of the week went by in a blur of anticipation. But that's also how he felt like a lot of time was going by now; he always had something to look forward to. Sure, he didn't have the ambitious big city job he'd had a year ago. He didn't have marriage prospects either, really. But these things didn't bother him. Life was good.

Midday on Saturday, Mark dropped Emma off at his coworker's house. The two young girls made fast friends. Hopefully that would last an entire night without incident. Emma waved goodbye to "dada", and Mark laughed, explaining that she had gotten in the habit of calling him that. Hopefully she'd learn "uncle" before it got too mortifying.

He and Kate drove two hours to a lake-side resort town. During the drive, he held her hand whenever he could. She was wearing a thin, patterned summer dress that fit her curves well. Even so, there was something especially sexy about her today, even with clothes on. Maybe it was because they were off on a romantic weekend getaway. They both knew at least some of what they'd be doing, with the entire weekend to themselves.

At the resort, they were just two tourists among many. No one knew them, no one knew they were brother and sister, as long as they didn't give it away. So for once they could be affectionate towards each other in public. It added an inordinate thrill to the merest peck on the lips, the littlest contact.

"So what now? Do you enjoy casinos?" Kate asked, as they set down their bags in the room.

"No, I can't say I like gambling much," Mark said, drawing close to where she sat on the bed.

He could feel the arousal in the rise and fall of her chest when he brought his lips to her ear, but then she pulled away.

"We have four walls and a bed back home. Might as well do something we can't do there." She reached out a hand. "Come on."

With her help, he got to his feet, bringing them face to face. He was starting to feel like she was acting distant. He tipped up her chin, and kissed her on the lips. She welcomed it and started to melt into his arms, her large breasts pressing against him through her dress. Just as they were heating up, she backed away from him, until they were just hand in hand.

"Later," she whispered, a promise. "Don't get a boner right now. We're taking a walk on the beach."

Out on the sand, she took off her shoes and carried them in one hand as they walked up along the sand.

"So is this some kind of test, to see whether I can still act normal around you?" he asked. There was something up, he just couldn't put his finger on it.

"No," she answered. Then she added, "Kind of the opposite, actually."

She took his hand, and brought them to a stop. "How would you act, if there was nothing at all wrong with the two of us being together?"

He put a hand on her hip. "Like...if there were no public indecency laws?"

"Ha. No, I was thinking more like...if the two of us weren't...you know."

"Well, in that case I'd be just as in love with you," Mark said.

It sounded corny even to him, but he didn't want to lie to her. He didn't want to hide how he felt, from the only person in the entire world who should know.

Although it was really hard to say for sure whether they would've been together otherwise. If the two of them hadn't grown up together as brother and sister, how else might there paths have crossed? If he hadn't been living with her, what might it have taken him to see the beauty in her? She wasn't not his type, clearly, but she'd been a bit of a stretch for him, in the beginning at least. Now his type had changed. Now everything had changed, and if she wasn't his type, then maybe no one was.

Rain started to fall, light and not unpleasant in the summer heat. They made it back to the room before they got too soaked, but they still changed out of the damp clothes. He caught Kate looking as he changed, but she didn't pin him to the bed and ride him like she normally would have. She was still being coy, but obviously not indifferent. Mark wondered what was up, but decided that he had already pressed enough. By the time the rain let up, they had missed the sunset behind a dark cover of clouds.

"Let's go out for dinner," Mark suggested.

"Sure. I think I saw a fish and chips shop..."

"Tempting, but....that's not much of a date spot, is it."

Kate looked a bit disappointed to turn down fish and chips. "Fair enough."

They got a table at a fancy place near the resort. Green tablecloth, multiple types of cutlery, with wine, steak, and seafood on the menu.

"What a year," Mark said, when they started digging into a shared slice of chocolate cake.

"And to many more," Kate said, making a toast.

"Heck yeah. To many more," Mark agreed, clinking her glass with his.

"I like that you haven't said anything about a fat girl like me eating a bit of chocolate cake," she said.

Mark shook his head. "I know how you got made fun of, growing up. I would never do that."

"Huh. You're right. You, of all people, never did. You certainly made fun of me for plenty of other things, but never for that."

"It's not like you were lazy or unhealthy or that you overate, no more than me," he said. "You were just born you, with a lot of your dad in you."

Growing up, Mark and Kate had always brother and sister, no qualifiers. That was how their parents felt, and that was how they referred to each other. So it wasn't often that they pointed out that they had each come from previous marriages. Even now, with everything that had happened between them, Mark wanted them to be more than brother and sister, but not to diminish what they had before. Having said it left an odd taste in his mouth.

"I just...need to know for sure," Kate said. Mark could tell that it took a lot of effort for her to say. "That there will be years to come, for us. Where we stand, where we're headed. For Emma, and for me, and for..."

"You aren't like terminally ill are you?" Mark asked.

"No," Kate said, half-laughing and half-crying. "Gosh no."

"If it weren't for...you know...our situation...Kate, I would kneel right here on this crumby carpet and propose to you. The life we have isn't what I would've chosen for myself as a stupid 23 year old, it's so much better. And I don't care if people start to talk about us, I'm not giving up on us until you do. Maybe not even then, I don't know. What we have is for life. Or it can be, anyway, as long as you want it."

As he went, he found out firsthand that it wasn't so easy to talk about this stuff honestly without tearing up a bit, without a tickle in his throat.

"I do," Kate said, and then realized what she'd said and laughed. "I do want that. For life. Or for as long as you do."

"Is it okay to kiss in a restaurant?" Mark asked.

"Maybe if you actually fake-proposed," she said. He searched her eyes for a hint of whether she was daring him to. "Please don't."

Mark knew that just a year ago, if his sister said "please don't", he'd probably do exactly that. But he saw the sincerity in her eyes. He wouldn't do that to her now.

Back in the room, alone together again, Kate turned and kissed him as soon as the door closed.

"Thanks for being patient with me today," she said softly.

"You should never expect any less," Mark said.

She unbuttoned his shirt, and he reached around her, undoing the back of her dress, as they hardly broke their kiss to come up for air. Then it was her breasts pressed hotly against his chest, and he felt himself starting to rise, felt her start to press against him, as they stood there making out.

"We paid for the bed too, right?" he joked. "I don't think I can stand for much longer, with where my blood's collecting."

She climbed up on the bed, where they hugged each other tight again, his lips doting on the exposed skin of her shoulder, her chest.

"Sorry if I'm taking this slow. Maybe it's silly, but I want this to be special," she said. He could tell by the way she reacted to his touch, it wasn't for lack of want.

"You don't have to apologize," he said. "I didn't know this anniversary meant so much to you."

"There's...something else," she said.

He propped himself up on his elbow to get a good look at her expression.

"You may have noticed that we're not in our house, so the normal rules don't apply..." She smiled slyly. "You don't need to use a condom tonight. Unless you want to."

"Are you back on the pill?" he asked.

"No, guess again."

"You got an IUD? It's not your time of the month? You're planning to get a morning-after pill? You've got six months to live?"

She shook her head with each guess, and finally interrupted. "I'm starting to get the impression you don't want to have a baby with me."

"...After just a year?" Mark asked, his mind reeling.

"Mark, I've known you literally my entire life," she said. "But if you're not ready, I understand..."

"No, that's not it at all," Mark said, still processing this revelation. "To be honest, I fantasized about it since the very beginning. There have been times when I almost couldn't hold back."

"Yeah, I kinda noticed that."

He went on, "But at first I thought it was just that, a fantasy. My horny brain fixating on the one thing it can't have. That's why I've started helping out with Emma. One reason, anyway. I wanted to get a taste of parenting, and see if I'd be able to handle it. I thought maybe it would scare me straight."

"If you think babies are a challenge, wait until she's a teenager," Kate said.

"Whoa. So that's why you had to know if I wanted us to last. What do we tell her?"

"I don't know. That I made another dumb mistake? That I got sloppy at the truck stop glory hole? Or maybe we just tell her the truth." Kate put a comforting hand on his arm. "Living with the two of us, I don't think we can hide what's going on from her forever. She's going to figure it out eventually."

This was almost too much for Mark to take in. The idea of having a baby with Kate--of becoming family in more ways than one--it had an almost irresistible draw on him, and that was what scared him. He knew his mind was addled with the possibility, and with her naked, voluptuous body, and the impending combination of the two. What he didn't know was whether this would still seem like a good idea when he'd wake up tomorrow.

He started kissing her again, and it wasn't hard for him to imagine her belly growing full with child again. He had seen the pictures during her first pregnancy, but even then she hadn't been quite the woman she was now. But to know that the child inside of her was his too, to be able to remember to the moment when they conceived, that would be something else. Mark found himself quickly becoming hard, and he could sense the urgency in her too.

Her hands reached for his shaft but he guided them away, fearing it'd be too much too quickly. Instead, she grabbed his hips, pulling him on top of her. At first, they just laid still there, with him nestled in her slit, kissing, savoring the moment. But her hips wouldn't stop moving under him, rocking her clit against him.

Reaching down between them, he guided himself to the precipice of her. He had penetrated her before, but this was the first time he was about to do so unsheathed. He looked into her eyes, giving her a chance to back down. She gave the slightest of nods, her hand on his waist pulling him close.

He sank into her, slowly, inch by inch. With every new part of her that he touched, he felt her react. A little jolt of pleasure that rippled through her nerves and muscles. It made him twitch and flare inside her.

At last they were conjoined, pressed tight against each other, the tip of his cock pressed about as deep into her recesses as it could go, her channel hugging and massaging his length. He had heard things about women after childbirth, so he hadn't expected it to feel like this.

He started to withdraw, but she held him in place, her limbs clutching his. "Don't. Let's just...stay here for a bit."

With her words, she clenched muscles deep inside her that made him gasp.

"But Kate...I'm not going to last long like this," he said.

She ran a hand through his hair. "You don't have to. That's not what's important to me right now. I just want to feel it when it happens. The moment that's going to change our lives forever."

Mark would have rather for the two of them to reach orgasm together, but the feeling of being inside her with nothing between them, the feeling of what she was doing to him, he couldn't resist it for much longer.

"I'm about to cum," he warned her. If there was still a moment to turn back, it was now. But his willpower alone wasn't going to be enough.

"I'm ready," she said.

"Oh my god," he gasped.

It was him pinning her to the bed, yet she was doing all the work. Deep inside her, he felt her muscles undulate around him. It was tender and delicate and yet nearly overwhelming.

He felt himself swell up inside of her. It might have only been seconds, but those seconds stretched like elastic, as they both anticipated what was impending.

His seed jetted into her. He felt the warmth fill her cavity and spread out around him. Knowing what it meant, knowing that it had likely reached every corner of her, where it could seek out its purpose, it drove him crazy, making him swell and pour more into her.