Mom Sits on My Lap in the Car

This is a rewrite of "Mother Sits on My Lap in the Car" by chris99999.

Major changes: I really liked the plot of the original story, but the execution was a mess. I made lots of grammatical corrections to improve clarity as well as major rewrites to make the story steamier and more realistic. Basically half or more of the original was gutted and replaced.

Minor changes: Body shapes, personalities, and family details changed to match my own family.

---

"He's published a new one. Have you read it?" Millie asked me.

"Not yet," I answered. I was going to, but I'd been busy. It was on my list of things to do.

"I wouldn't bother, it's not as good as his other ones. In fact, it's really unrealistic. It was so unbelievable I couldn't get into it."

That was a surprise, because he was our favorite author on Literotica.com. I realized that she must be joking, but when I saw her face I knew that she wasn't. I was now curious.

"What's wrong with it?"

"It's not realistic. You can't have sex in the back of a car without the driver noticing. You'd hear them, and there might also be a smell of sex in the confined space. It's insane to think that you could get away with that!"

Still skeptical, I answered, "I'm going to read it, and we'll see if I agree with you."

My younger sister Millie and I have been sleeping with each other for years. That's a long story, but it all started with us trying to find things to weird each other out, except we ended up getting really turned on by this incest erotica author instead.

This author still knows how to push our buttons, but apparently Millie hated his newest story. It was called, "Mother Sits on My Lap in the Car." It took me about 30 minutes to read it, and as soon as I'd finished, she was asking for my opinion of it. I was going to give it to her, but she wouldn't like what I was going to say.

"It was good. A clever story that was well-written, with some steamy sex. What more did you want from the story?"

After giving a deep sigh, she said, "Some realism! They're bonking like crazy, but the driver is oblivious to what's happening. There's absolutely no way anyone could do that without getting caught! That's why I only gave it three stars."

"Three? That's way too harsh. Yeah, it required a little suspension of disbelief, but it was realistic enough to look past it. The radio was on, windows were rolled down, and that TV was blocking the dad's view. Maybe most moms would move around or whatever to change out the situation, but you never know what you'll do when things start bumping and rubbing and you get horny enough to stop thinking straight."

"But that's my point though!" She said, still upset. "There's no way any mom would let it go that far in the first place. But even if it were husband and wife, the driver would notice something was up whenever he tried talking to them or when they unloaded the car."

"I don't know, it seemed crazy, but still believable enough for me. Plus, it was really hot. I'm giving it a perfect 5 stars."

He had written a few before that just didn't do it for us, but none that had made her this upset before. She was so angry with it that she kept arguing with me for the next two weeks, trying to make me admit she was right. But I got annoyed with it, so I dug in deeper, actually changing my argument to say I thought it was very realistic, if only to make Millie mad. Meanwhile she dropped her rating of the story to a 1, probably just to make me mad. After a couple weeks, the author posted a new story about a brother and sister camping together. Millie loved it and we dropped the topic of car sex... for a while at least.

--

A few months laster, our parents were moving. They timed it so we would be home from college to help. Dad rented a moving truck, and we spent a week loading it up. The plan was for Dad and one of our uncles to take the truck to the new place 3.5 hours away, Mom and one of our aunts would drive our parents' car, and Millie and I would drive separately. Then after everything is unloaded, Millie and I would drive our aunt and uncle back to their house on our way back to college.

However, Dad went cheap and rented a truck that was way too small. Two sizes up would have held everything, but because of his mistake, both cars were now also filled to bursting. Mom is an expert packer, but no matter how she rearranged everything, we were still one seat short to fit everyone.

Eventually Dad got fed up and hopped in the truck's driver seat. My uncle shrugged, hopped in the passenger seat, and the truck took off. My aunt's anxiety got the better of her, and she hopped in my parents' car to quickly follow after them. That left Mom, Millie, and me to squeeze into 2 open seats in my car.

Mom called my aunt, asking her to come back and drop off her house keys so one of us could stay at her house for the week, but she didn't want to turn around. I also chimed in that we would figure it out, but that was more because I was excited to break in a new home (and new bedroom) with my hot sister.

Mom hung up the phone, pissed. "Ugh!! How the hell are we supposed to do this if I'm the only one trying to figure anything out!"

"Don't worry, Mom, we'll figure something out," I said reassuringly. "Worst case, maybe someone will have to sit on my lap." I gave Millie a playful wink.

Her face was a picture, astounded. Then she had a thoughtful, mischievous look in her eyes.

Mom said, "You know, we just might have to do that!"

Millie eagerly agreed. "Why don't we move everything so the back seat on the passenger side is the one that's free? Then maybe we'd be able to push the passenger seat forward and give the people sharing a seat in the back more room."

Mom, still angry, got to work. I whispered to Millie, "Holy shit, are you about to fuck me with Mom in the car?"

She looked at me like I was the world's biggest idiot, then burst out laughing. Mom glared at us, so we helped her. When we finished, it actually looked decent. Not roomy for two people, but enough room that we won't be terribly cramped. But that meant boxes and bags were jam-packed everywhere else, and there was no way the driver would be able to use the rear-view mirror, let alone see into the back seat. It was perfect.

Mom was sweaty from rearranging everything so many times this morning, so she found a spare outfit in a bag and went inside to change, letting Magnolia and I talk again. She said, "You dumbass, if I sit back there and we have sex, I know for a fact that we would get caught, and I'm not going to let our Mom bust us. No, you're going to test out your dumb idea and have Mom sit on your lap."

Now it was my turn to look astounded. "No way!"

"It's just a little experiment. We'll drive for a while like that, and I'll prove how ridiculous that story was. If you make a noise or anything, I'll bet that I'll be able to hear it, but it won't even go that far. I know how your animal brain works; Mom looks just like an older version of me, and you've got this stupid erotica story on your mind, so Mom sitting on you will give you a hard-on. When she feels it, she isn't going to let you fuck her like in your dumb story. She'll ask me to change places with you, or for you to sit on her lap, or something like that, and that will be the end of it. That will prove how unrealistic the story is."

After giving a deep sigh, I said, "Okay, you win. But if this is such a big deal for you, we should make it a bet. What do I get if I win?"

She looked playfully thoughtful. "Well obviously you'd get your rocks off, but Mom would be the one doing it."

I laughed, "Weird, but no, there should be something on you if you're wrong. How about you finally make a video with me? Blowjob, sex, and anal."

She laughed. "Wow, you're really pulling out the big guns, huh? No anal, not in a video, but okay that's fair. So if you get that then... if I win..." Her face lit up, "You have to give me oral every day for a month, and you can't cum for a month."

"No way! That's way too harsh. Oral for a month and can't cum for 2 weeks?"

"No deal. Still a month, but in your video, I'll swallow the blowjob and let you creampie me."

Those were two things I never got to do, despite us being together a long time and her being on the pill. "Deal!"

I offered my hand, and we shook on it. She reminded me, "Remember, you have to get her to do something sexual, and you can't get caught by me."

Mom came out of the house, locking it up for the last time and giving it a teary-eyed goodbye. She walked to the car and Millie spoke up. "I'll take the first shift driving. Just let me know if you two get too uncomfortable and we can switch around."

Mom sighed, her anger subsided and she was now resigned to our fate. She looked at me apologetically, "If I'd known I'd be sitting on your lap, I would have tried harder to dig for different clothes." Her shorts were very short and loose, so I could see a lot of leg. But they have a liner inside, so she never wears panties with them. She probably didn't think anything of her shorts, but the bigger problem was her top. It was low-cut and loose-fitting, and she was very big-breasted. "I couldn't even find a bra, but the one I was wearing was soaked with sweat."

"No worries, Mom, this is just what you normally wear around the house, so it's no big deal." Except it was a big deal because she'd be on my lap. I looked at Millie. She gave me a sour scowl, knowing I was off to a good start.

We sat down and I confirmed that Millie couldn't see a thing. When I looked down over Mom's shoulders, I could see a lot of cleavage.

As we drove off, I looked away from her. This was going to be difficult to make it seem natural. There was already a stirring in my underwear.

"Can you hear me okay?" Millie asked, fairly quietly.

She got a quick yes from Mom, and I could picture Millie's shit-eating grin. She asked in a low voice, but despite the boxes on the front seat, and all the other stuff that was a barrier between us, we had clearly heard it, which means she would also be able to hear us pretty easily.

Millie was now eagerly waiting for Mom to ask her to change places, but that would only happen when I'd got an erection.

To spite her, I was doing my best to stop that from happening, just to prolong it and make Millie wonder. But it was difficult. When the road got rough, it became impossible as the steady rumble rocked and bumped her gently on my lap. As my cock started to grow, I had a sudden thought, and it worried me. We had assumed that Mom would react calmly, but that might not be true. Feeling my cock pressing into her might freak her out. I was an idiot! I should never have agreed to this.

She was now moving her bottom. She must have felt it pressing into her, but thankfully she seemed like she was just trying to ignore it, shifting to find a comfortable position. Very soon, I was going to be in big trouble. But then she settled back down and didn't say anything. It looked like she was going to ignore it. Despite my bet with Millie, I wasn't prepared to die today, so I couldn't gather the nerve to make the first move.

It took me a while to realize what she was doing. At first, I thought it was accidental, but it wasn't. It was deliberate. She was rocking herself on me. Only slightly, but just barely enough for me to notice. I probably wouldn't have noticed at all except she was definitely repeating the motion on slow, regular intervals.

My mom wasn't ignoring my cock, she was enjoying it!

"I'm stopping for gas and coffee," Millie said.

That was a relief. This seemed like it could be happening, and now I wasn't so confident anymore. I needed a break to think straight. It wasn't too late to back out and change places.

When Mom went to the restroom, Millie was eager to talk. "I'm surprised that you couldn't get it up. Normally, just looking at a pair of tits gets you hard. I thought that her sitting on you would have got you excited."

I lifted my T-shirt up so that she could see my crotch. I wasn't as hard as before, but I still had an impressive bulge. "I got an erection, but she didn't complain. In fact, she was enjoying it, so that's why she didn't ask you to stop."

It took her a few seconds to comprehend that. Now she was shocked, but then she quickly became excited.

"The dirty bitch! Enjoying it how?"

"Just rocking on it every now and then. I thought she was just getting comfortable, but it was definitely more than that. But she might have just felt stuck in the moment. You should offer to switch places, just so we know for sure that she's not feeling forced into a situation she doesn't want to be in."

"Oh, getting cold feet now? Ready to lose that bet?"

"I'd rather lose than make her feel trapped."

"Fair." Millie said, before shouting over my shoulder, "Welcome back, Mom! Want to drive?"

Mom looked sheepish, grabbing her arm and then the back of her neck nervously. "I'm okay actually. I didn't get a coffee, and I might take a nap or something."

I guess that was our answer. Millie jumped into the driver's seat before I could stop her, and the look on her face told me that she was staying there. I shrugged, smiled, and climbed into the back seat.

It wasn't long before my cock was active again, and not much longer before Mom started moving again.

"Is everybody okay in the back?"

Mom answered with a yes, but I kept quiet. I wasn't in the mood for talking. I was more focused on the woman sitting in my lap, moving her bottom against my swollen cock. Part of me wished that the woman that was doing it wasn't my mother, but Millie had a point. My sister was smoking hot, every guy we knew thought so, and Mom was just an older version of her. A little bit more in the belly and thighs, and a lot more in her ass and chest. The guys I knew joked about each other's sister's all the time, but my mom was one of the few that my friends thought was really hot. When you're a teenager, there's always at least one mom in your group of male friends that everybody thinks is a MILF. For me, and my friends, it was my mom. She didn't wear revealing clothes, or act inappropriate, when she was with them, but her beauty and body were there for all of us to see, and to admire. All of them wanted to fuck her! And ever since Millie and I discovered our incest kink, I was right there with them, wanting to bang my own mom.

"My shoulders are tense. Would you please massage them?" Mom asked me.

I was going to say yes, but before I could, Millie spoke. "You're making Mom uncomfortable? Give her a massage and fix it!"

Her eagerness to get us busted was getting annoying, but I channeled my inner Phineas & Ferb and instead of telling her off, I simply kept the peace by playing along.

My hands were now on Mom's shoulders, rubbing them like she'd asked, but my eyes were looking at where I'd like them to be. On her gorgeous breasts. But I was still too nervous to make a move, so gazing at them was all that I could do.

After a few minutes, Millie spoke up "Hey guys, looks like there's a bunch of construction ahead. The detour doesn't look like a well kept road, so for a few miles it might get a little bumpy. You might want to wrap your arms around Mom to be her seatbelt."

To me, the road didn't seem any different, so I kept my hands on her shoulders. Mom felt otherwise. "I think we should do what Millie says. It will be safer if we do."

I wasn't sure if this was Mom being a sensible mom or if she wanted to feel my arms around her. Either way, I was grateful for the opening. I put my hands on her waist, still a little too nervous to wrap her up tightly.

"Is he holding you tight?" Millie's voice sounded perfectly innocent, like she was genuinely concerned for our safety, but I knew she was just trying to help me out so she could win our little bet.

"Not at all! Come on, hold me tighter." Mom grabbed my hands and pulled them across her stomach. I wrapped around her torso, squeezing her tight and pulling her back against my chest.

Just as I started to wonder if Millie made the whole thing up, the road got pretty rough. We bounced around quite a bit, and Mom took full advantage of it to start grinding into me much more overtly. Her breath became labored, and she almost seemed to melt into me as she deliberately pressed our clothed privates against each other. She still wasn't addressing anything directly though, so it was still possible that she was trying to be sneaky and intended to stop as soon as the road got smoother.

"Shit!" Millie yelled as we hit a really big pothole. Everything in the backseat bounced into the air, especially us. Apparently I would have been a pretty bad seatbelt for Mom because as soon as we went airborne, my arms failed wildly.

When we landed and got settled back in our seat, I realized my arms were now crossed, and instead of grabbing Mom's stomach, they now firmly gripped her huge tits.

Instinctively, I let go and moved my arms down, but I immediately regretted it. That was a perfect opportunity to feel her up and win my bet, but I wasted it.

"Um..." Mom said, hesitating. I prepared myself for a lecture, but instead she said, "I think it actually felt a little safer when your hands were up higher."

Millie scolded, "Sorry about that bump, but just do whatever Mom needs to stay safe and comfortable. And don't make me have to tell you again, I mean it!" There was anger in her voice, but I could tell that it wasn't genuine. It was all part of the act. It was to give me an excuse for doing it.

It was now decision time. This was more than what could be considered forgivable. This was a blatantly sexual act, and our relationship could never be the same. I could put a stop to it now, but Mom was willing, wanting me to touch her breasts, and Millie was begging me to do it. This was a situation that most men could only dream of, but I was still in two minds about doing it.

A righteous man, with a lot of willpower and self-control, would be able to resist the temptation. But I wasn't that man, so after taking a deep breath to steady my nerves, I lifted my hands.

I was cupping her large mounds, the breasts that I'd been admiring for years. Sometimes Millie would wear Mom's clothes and we would roleplay situations like this, but it was nothing compared to the real thing. They were heavy, soft, and felt like heaven. Millie's were firm and amazing to look at, but Mom's were way more fun to play with. Even though her back was towards me, I knew that she was smiling, because she'd gotten what she wanted.

She let me explore them, which I did til my heart's content. I wanted to savor every moment since I'd been dreaming of this for so long. I inevitably wanted more. When my hand went down the cleavage of her top, she jumped a little. That made me smile, because she must have known that I was going to do that, but she was still expecting me to be the voice of reason here, not the one to push things further.

I tried moving my other hand inside also, but even though the top was loose, it wasn't loose enough to easily get both my hands in through the neck hole.

"It would be easier if you just take my shirt off." Mom said it quietly, but not a whisper. The road was noisier here, but it could have still been loud enough for Millie to hear. I didn't want to lose the bet, so I shushed her, but I also didn't hesitate to obey, yanking her shirt over her head as she raised her arms for me.

"Would you like to take a break? I can stop." Millie chimed in cheerfully. That got a quick no from both of us, and I could tell that she was trying not to laugh. She knew perfectly well that we didn't want to stop, she was just teasing us. Which probably meant she heard Mom and I had lost the bet, but I was going to be cautious anyways.