Keeping Our 18th Birthday Promise

This is my first story for Literotica. All characters are 18 or older of course and any and all thought or actions of sexual nature occur after that age. Any and all comments are encouraged and welcome. I've heard it said truth will always be stranger than fiction because fiction has to make sense. I'm not going to say one way or the other but if you comment I'd also be curious as to whether you think this story actually could be true and why or why not.

The events of these last few weeks involving me, my sister and our parents have been flat out, mind blowing, fantastic for sis and I. This then is the story of how our present wonderful situation came to be.

It all started with our 18th birthday. Well really the day after. Until that fateful day we'd never thought of one another as any thing other than brother and sister. Sis and I are twins, she's older by about five minutes. We'd been taking extra courses for college credit the last year and a half of high school and had both graduated at the beginning of the summer.

It was already early September and college started for both of us in two days. Sis not too far from the folks small farm and me at the agricultural university across the state. Even though we'd never really been separated before, having grown up as playmates and close as twins so often are, we weren't too concerned as we'd still be able to visit the folks fairly often.

Only three more years of college and we could put our longer term plans for turning the farm into a real business into action. We thought being able to start our own business at 21 would be just fine.

We were a later in life sort of surprise for our folks and were 11 years younger than the youngest of our brothers who all now had families of their own some distance away. Mom had explained it when we were older. She was 42 at the time and thought she was finally over menopause. She and dad had celebrated with gay abandon.

A little too much celebration and way too much abandon apparently as she turned up pregnant within a month. At her age there was some concern that her eggs may have been past their best used by date.

In due course though we both showed up in fine condition. Growing up together on a small farm on the far outskirts of town was nice and we were happy to be there helping mom and dad. Sis had decided to major in business and culinary arts and I was going for an agriculture major.

The town had grown much closer to the farm in the last few years and local tourism picked up as well. We planned on taking over the farm on a more businesslike basis with a bed and breakfast and small bakery attached. We had the space for the new buildings and mom and dad were all for it.

There was even plenty of room for us to raise families of our own if we either ever found that special other. So far though not even close, just a few dates with various boys and girls in high school. In spite of all the stuff you hear about the wilder side of teenage life we like most were still virgins.

For us this might have been because we knew our parents had both both been virgins when they got married at 20 for mom and 24 for dad. Even though they were children of the 70's that was just the way it had worked out for them and I guess it still looked good to us.

It would be a while before we found out just how much of that 70's open attitude about sex they had been immersed in was still part of their seemingly conservative makeup but more about that later.

Our 18th birthday party was really special. Our older brothers and their families filled the house with people and kids for a grand cookout that ran well into the evening before they all headed home.

Mom and dad slept in the next morning while sis and I tended to morning chores. Usually this was feeding the livestock and gathering eggs after turning the chickens out of their coop.

We'd always had a variety of smaller animals about the place but in the last month dad had added a couple of plow horses he was planning to use on few adjoining acres he'd also just purchased. The pair of them, Bob and Sue were in their corral at the moment and we'd turn them out later.

As we headed back to the house with eggs for breakfast we both grabbed a big handful of long, fresh, green grass to give them as we passed by. It had become a thing for them to come over for grass and petting.

We set the eggs down and stepped up to stand on the bottom rails the better to hold out the grass.

Something was different this morning though. They both completely ignored us. Sue was just standing there a bit stiffly with her tail arched. Bob was dancing about a bit and sniffing at her tail.

"That's odd," said sis.

"Yeah," I agreed.

If we had had Bob's sense of smell we'd have known what was literally in the air. You'd think a couple of farm kids would have been quicker on the uptake. In our defense we'd seen plenty of chickens, goats, dogs and so on going at it but they were all much smaller animals. We'd never even had cows.

All of a sudden as Bob reared up on his hind legs his shaft which had been hanging loose suddenly stiffened into two feet of pure maleness about three inches across at the business end. Taking a half step forward he lowered his front legs over Sue's shoulders and just rammed the whole thing straight into Sue's waiting cleft!

We were simply transfixed! Pure, erotic poetry in motion on a huge scale. The big muscles in Bob's haunches contracted into stark relief at the end of every nearly foot long stroke as he pumped her. After half a dozen he held himself still as deep into her as he could go while those haunch muscles kept flexing strongly.

Then almost as quickly as it takes to tell it Sue stepped forward. Fluid streamed from her opening as Bob's now limp shaft slid out and the deed was done. Just like that. Wow!

What I had just seen was burned like a photograph in my mind's eye. As it turned out sis was affected the same way.

I turned to look at sis as she turned to look at me. Her eyes had to be as big around as mine were. It took a few seconds of just staring at one another for me to realize I had a massive erection building. I don't know what sis felt but it must have been similar because we both began blushing together.

We were distracted by the realization the grass was being pulled from our hands by a couple of friendly horses who also wanted petted. Thank goodness for friendly horses. It gave me time to be able to stand up straight without embarrassing myself. When they were satisfied we picked up the eggs and resumed our walk back to the house.

We were about halfway back when sis was first to break the silence. "Now that was purely awe inspiring little brother wasn't it?"

"And how sis, and how. They sure showed us how to do it didn't they," I agreed.

And then it hit me, I don't know for sure where it came from. I'd never really thought about anything faintly like it before but there it was plain as day. What I'd just seen in the corral was replaced with an image of the two of us in the same place doing the same thing!

Not the sort of fantasy I'd had before about similar things with a generic, possible, future unnamed girl.

No this was sis out there with me. I'd never seen her naked even a little bit. Just hadn't happened but that little fact didn't stop my imagination once it was tripped off.

Sis takes after mom, whom I'd also never seen naked nor thought to either, short, stout, very firmly well rounded with 40C boobs and size 8 undies. Hey, I helped do the wash too. Sis has long, fat blonde braids, blue eyes, freckles across her nose and the face and temperament of a very friendly bull dog. That voluptuous plump package was the picture my mind supplied bent over in front of me.

I must have stopped walking right after my question to her.

"Hey, earth to bro, yes they sure did show us," she replied and waved a hand in front of my bemused expression. "What's going on in there anyway? Wanna share?"

Oh yes I wanted to share but that thought had me blushing like crazy. Still we'd always shared everything. If for no other reason we had long ago found we really couldn't fib to one another anyway.

"Oooo, it must really be something. It just has to have something to do with what we just saw," she teased. "Come on, give. Tell me."

Okay, now I had to tell her. But how could I say what what I'd seen told me I wanted to do? I took a deep breath and just jumped into the deep end.

"All right sis, but remember, you asked," I began with as serious a look as I could manage. A brief pause and she nodded firmly.

"Well I've just had a beautiful, beautiful vision. So here's a question for you then. If that had been me instead of Bob and you instead of Sue could you have stood there like her and had me do what he did?"

A long pause as I looked into those blue eyes above her freckles and then she answered. "You know. we must be twins. I think I had sort of the same idea so I'd have to say yes. Most definitely yes. For my very first time I can't imagine any better way to do it and no one else I'd rather do it with. Yep, glad you asked. That's my final answer."

For some reason I found I had to push for absolute clarity.

"So not just imagine but you'd actually do it that way with me, your brother, for real?," I persisted.

A briefer pause. "Yeah. This isn't just imagination. What we just saw has cleared up something for me. If I don't find 'the guy' pretty soon that's exactly how I want my first try at making babies to happen. Just exactly like that, with you bro, with little old you," she said with a twinkle in her eyes and a smile from ear to ear.

I had to gulp a time or two before I could continue.

"Any time you say sis. I promise. Any time."

"Cool. Now all we have to do is pick a time."

"We do?," I asked brilliantly.

"Yes we do. A girl's biological clock only runs for so long after all. Let me think."

After just a moment she continued. "I've got it. We get our degrees and start the business in three years. We'll be 21. That's about when mom and dad started having a family so there it is. You just promised you would. What do you say to the evening of our 21st birthday as the time for that promise to come due?"

Oh my, my very own sister, she was dead serious. But as the reality sunk in it just didn't matter anymore that she was my sister. For some reason this was just something we had to do. I stuck out my right hand.

"Let's shake on it then and call it a done deal."

Her hand came up and shook mine firmly with no hesitation at all.

"Well I'm so glad that's settled then. Now let's go get breakfast on", she said and headed for the kitchen. A very practical, well focused gal my sis.

She just bounced off to the kitchen, braids swinging and her big broad backside too. I'd never really noticed the seductive way it swayed counterpoint to those long fat braids. Timeless, classic, young farm girl, that's my sis.

That lovely backside suddenly made it more difficult to walk upright again. Oh well, small price to pay for what it promised in the future. Besides I was really enjoying following her back to the house.

We took off for college the next day. College was good for both of us. Home sickness and separation weren't a problem at all. Texting kept us in touch with one another and the folks back home. One or the other or sometimes both of us got back to visit mom and dad every other month or so for a weekend or most of the school holidays.

It was at our next birthday the tradition started. After we blew out the candles together for our wish, as we had since we were children, we stood and shook hands. We knew what our wish was!

When we shook hands on our twentieth birthday sis gave me not only a firm handshake but the most loving grin I had ever seen. As far as she was concerned we were still on for it next year. So was I for that matter but it was sure good to know what her feelings were.

Finally! Our twenty first birthday arrived.

Sis had fully grown into stout, healthy womanhood and I'd put on a fair amount more muscle myself. We'd graduated, had our degrees and were raring to go. Everything we'd planned was to start with our long awaited visit to the corral.

As we gathered eggs that morning I just couldn't stop ogling sis's broad backside when she bent to get to the eggs in the lowest nests. I'd never seen it outside blue jeans but my imagination was going crazy.

I was having to stretch to get to the highest nests. Apparently I wasn't the only one copping a look.

"Is that a banana in your pocket or are you just really glad you'll be seeing me in the corral tonight?"

I nearly dropped the eggs as I laughed. "Don't do that. But it's no banana and yes I am so glad I'll be seeing you tonight in the corral. You are one birthday present I really want to see completely unwrapped sis."

She gave me a very hungry look. "Mmmm. I am ready and then some to go for it all. I want to see my present all unwrapped too you know. At least for a little bit till it gets behind me to give me my real present brother."

"Uh sis, about that. I mean I'm as ready as I can be but, well, I've heard that the first time can be kind of, well painful for girls. So I want you to know if we can't just haul off and do it like Bob and Sue the first time I'm okay with taking it slow and easy if we need to. The last thing I'd want to do is hurt you."

That got me me a very knowing look. "Do you remember that nice, big cucumber salad we had early last month?" Talk about a non-sequitor.

"Huhh?" I replied intelligently.

She chuckled. "I made sure none of that unbroken hymen stuff could get in our way. Mr. Cucumber was a really big one and he and I did a really good job. You were right to be concerned though. It was pretty painful at first but a lot of shoving and pushing took care of things. I've healed up quite nicely. So really, really prepared you see." A very direct, practical girl my sis.

I already knew better than to ask her about getting pregnant. Some time ago she had made her opinion on that quite clear. She wanted her first time to be totally unprotected. "Good old fashioned baby making sex." as she put it. She said if she got pregnant then all that meant was she'd have a baby so she didn't see where there was a downside.

"All right then," I said and walked hunched over most of the way to the kitchen watching her hips sway.

Since it was our twenty first birthday and our homecoming to run the farm too the whole family showed up. We had a picnic cookout that lasted into late afternoon. We'd had one last firm handshake, looked deep into each other's eyes and unwrapped presents.

I got a fine smile from her as she unwrapped mine. A six inch very obviously anatomically correct bronze stallion. I could not fail to notice she held it with her little finger crooked firmly around it's manhood. Then I unwrapped hers. A lovely white well muscled ceramic mare with her tail raised.

When I set the mare on the table for all to see she of course placed the stallion nose to tail behind her.

It was just full dark when our older brothers and their families left. Mom and dad were next and wished us a good evening as they headed off to bed. Little did they know how good the evening promised to be.

They'd also given us a truly nice present and weren't even aware they had. They were taking off in the morning for a whole month's vacation for the first time in quite a while. This of course left us all alone to start in on our plans for the farm, never mind our plans for one another.

When we heard their shower start we knew it was time to keep our promise at long last.

As I looked across the room to where sis stood between me and the front door she gave me a huge smile. This was one of the rare occasions where instead of jeans she was wearing a light sort of peasant sun dress that reached to mid thigh. I could follow the curve of her fat calves to the fullness of her thighs as they led out of sight to where paradise lay.

I'd been pretty sure she had had no bra on under it but it was a little hard to tell. The clue was that the straps seemed to be taking a bit more of a load than they should.

Reaching up slowly she slid her right thumb beneath the right hand strap. Just as slowly she slipped it over her shoulder and let it hang there. Then just as slowly she used her left hand to slip off the left hand strap. Letting it go as well she just stood there with her arms relaxed at her sides.

Her dress hung there supported solely by friction on the top of those full 40C's. She must have been practicing because all she did next was say, "Well brother of mine?" and shrug slightly.

The dress slid straight to the floor and pooled around her feet.

I was speechless at the sight. My occasionally fevered imagination had been doing a pathetic job compared to the reality before me. I was frozen just staring at her generous curves but my gaze was torn between those gorgeous boobs with their huge nipples standing right out for most of an inch and the dense, lush blonde triangle that covered my most immediate goal.

She toed off her sandals and stepped barefoot out of the dress.

She cocked her head to one side and repeated, "Well brother of mine? You really need to get moving. You know just where you'll find me."

Pressing her right fingers into the blonde muff covering her slit she withdrew them to reveal a thick string of clear stickiness that separated and hung for about a foot between her knees as it slowly headed for the floor. "I really am ready you see." And with that she turned and headed for the door.

At last I got to see the full spread of her beautiful, broad backside I'd been imagining for so long. My dick had been engorged painfully for a while but this just plain made it hurt. "Why am I still standing around with my clothes on?" my mind asked.

I practically ripped my shirt off and flung it. It was a good thing I had those cotton briefs on or I'd surely have caught my shaft in the zipper so tight it was in there. I almost expected to hear "sproing" as my dick leapt out. I shucked pants and briefs in one move only to discover when they hit the floor I still had my shoes on!

Darn! Sitting quickly to tend to that oversight I looked up to see sis start switching her tail the last few steps to the door. Wow!! How had dad described that magical motion some years ago? Oh yeah. "Body by Fisher, bearings by Timken." Boy was he right.

By the time I got my shoes off the front door was empty and open. I headed straight out as fast as I could.

We had a full moon. When I got to the corral I had to pause to take in the sight that greeted me. It was just perfect and I wanted to remember it always.

There sis stood. She'd put a hay bale in the middle of a pool of bright moonlight and was bent over it, waiting. Her long braids hung down by her arms. Her breasts hung in the shadow beneath her like cantaloupes except where their sides swelled out into the moonlight emphasizing their firm roundness.

Her tummy hung just low enough for it's lovely downward curve to complement the rising upward curve of her hips. She was some sort of earth mother goddess waiting for her man to do with her the most primal thing for which they'd both been designed.

It was time for me to take my part in the picture before me so into the corral I stepped.

I walked to where her head was above the hay bale and stood facing her. When she raised her head the tip of my shaft was practically beneath her nose. I wanted her to see what she'd been waiting for before she received it.

Leaning just that little bit farther she placed her half open lips right on it's tip, extended her tongue and gently licked the clear fluid from it. I wasn't that close to climaxing but my shaft had a mind of it's own and bobbed up in surprise hitting her right on the nose.