Mum and Dad broke up for the last time shortly after that.

It's not a great thing to happen to any family at any time, and wasn't at all unexpected, but for it to happen to an eighteen-year-old girl who was studying for some of the most important exams in her life, was icing on what was already a tough cake to eat.

Mark and I were not the only residents of our street to overhear their last and loudest row and were probably not the only ones to welcome what had been the inevitable outcome for many years.

As an argument, it had followed the depressingly familiar pattern of most of their previous catalogue of rows, with accusations of flirting and infidelity thrown liberally from both sides. The difference this time was that, when Mum screamed at Dad that if he couldn’t bear to live with her, he should go and stay with his girlfriend, Dad simply told her he would do exactly that, and left.

For the next month, supporting Mum became a full-time job, outside of school hours. Though she still kept going to work, her self-confidence fell and her alcohol consumption rose, she went to bed earlier and slept in longer.

Mark and I were there for her throughout but were very pleased when one evening she announced that she had accepted an offer to go to dinner with a colleague from work.

We were more pleased to learn that the colleague was male. We were even more pleased when the dates became regular and lasted overnight.

During this time, Mark and I shared a bed with increasing frequency, his hands bringing me illicit pleasure many times. When my period arrived, I of course did not want his hands anywhere near my vulva, and expected to spend the week sleeping alone, but my brother had different ideas.

“Please Annie,’ he begged as we spooned together late one Thursday night.

Though still in my short nightie, a tampon was firmly in place in my vagina and I was wearing large, unattractive white cotton knickers.

“I can’t,” I protested. “I just can’t do it yet. I’m not saying never I’m just… Please, Mark.”

You can guess what my brother wanted. Denied access to my vulva he wanted me to repay all the pleasure he had given me by playing with his erect cock. I had quite literally never touched a boy’s erection before, had no idea what to do and being on my period, felt too dirty to try anything so adventurous.

“It’s only fair, Annie,” he moaned. “Just reach behind and touch it. It won’t bite you.”

He was right and I knew it. Our relationship had been all about me so far, but I was too young and too inexperienced to take the next step.

“Maybe next week when my time of the month has finished,” I tried, desperately trying to put him off.

An awkward silence fell. Mark continued to stroke my arms, sides, boobs, and buttocks but as I had asked, his fingers stayed clear of my vulva. This allowed me to feel what was making me so nervous, the pressure of his erect cock against the underside of my thighs.

“I’m sorry,” I said sadly. “I’m just not ready for it yet.”

“Don’t worry,” Mark whispered into my ear. “We’ll just cuddle, okay?”

“Okay,” I replied, relieved.

And cuddle we did. No words necessary, I lay quietly in my brother’s arms, his fingers slowly stroking my skin in the darkness. I felt warm, loved, secure. I began to doze.

A short while later, I became aware of movement behind me and a repeated, light, not unpleasant pressure on the back of my legs. It took a while to realise that it was Mark, moving his hips slowly forward and backward, rubbing his cock against my thighs.

“Mark…?” I whispered

“Shh! It’s okay,” he returned my whisper.

“But I’m not…”

“I know. Trust me!

I felt his fingers on the back of my thigh, then moving down to my knee. Then my upper leg was gently lifted, and my brother’s erect cock slipped between my thighs, high up against the gusset of my panties. A moment later, my leg had been lowered, trapping Mark’s firm shaft between the soft flesh of my inner thigh and my cotton-covered vulva.

It felt very strange, almost frightening but at the same time, very arousing indeed. No boy’s erect cock had been that close to my virgin vagina before.

Then, before I could adjust to its presence, Mark began to move his hips back and forth, sawing his cock between my legs, rubbing its upper side against my dampening vulva.

It felt so exciting and arousing that I began to tremble immediately.

“Do you like this?” Mark hissed.

“Mmm!” I mumbled, too aroused to speak.

Mark began to thrust gently and rhythmically, his shaft rubbing my outer lips through my panties, his hips nudging my buttocks every forward stroke. Although I was unquestionably still a virgin, an instinct deep within me recognised this was something like sex. It also told me this really should not be happening but the pleasure I was feeling easily over-rode any qualms.

Mark was clearly enjoying it too if the gasps and sighs coming from behind my head were anything to go by. With every stroke, they became louder and hoarser, and the pace of his strokes grew faster too.

Push-push-push-push!

His hips pressed against my cheeks.

“Huh-Huh-Huh-Huh’ his breaths came in soft gasps.

Then, without warning, I felt Mark’s hands grip my hips hard, his fingers dug into my flesh and the pace of his strokes grew much faster and less rhythmic. His breaths became grunts too.

Dimly aware that something had changed, my body went stiff, my legs gripping his shaft even more firmly.

“Oh God, Annie I’m…!”

Mark’s voice was barely a croak as his cock, pressed high between my thighs began to throb and pulse against my vulva.

“What…?” I stammered.

I could feel his erect cock beginning to soften between my thighs, then slip backwards and away. A moment later I became aware of something warm and wet running over my thighs.

Then it dawned on me what had just happened; my brother had just ejaculated all over my legs, panties, and bedsheets. There was a long, low sigh from behind as Mark’s breathing slowly returned to normal.

Not long after, I could feel his erect cock beginning to soften between my thighs, then slip backwards and away. I had literally no idea what to say or do so I simply lay there, feeling a stream of goo running down the front of my thigh. Nothing even close to this had ever happened to me or even near me.

There was a silence. Mark’s body stopped shaking and he cuddled me close while we both tried to take stock of the situation.

“Did I hurt you?” Mark asked anxiously, his breath warm on my neck.

I shook my head.

“It felt really nice. At least most of it did.”

There was another pause, during which I became even more aware of the mess on my legs and bedsheet.

“Is this semen all over me?” I asked, unsure whether to be angry, revolted, or pleased.

“I’m sorry, Annie,” he said. “I didn’t mean to cum on you. I couldn’t help it. You’re just too sexy.” He sighed. “I’m afraid your bed’s a bit of a mess too.”

The idea that I was so sexy I had made a boy cum, gave me a strange, unfamiliar thrill, but the slimy mess on my body and sheets was a lot less pleasant.

“I’ve never seen a boy cum before,” I whispered. “Does it hurt? You sounded in pain.”

Mark chuckled.

“It’s a kind of pain but it’s the best kind,” he said. “It’s best of all if you’re having real sex.”

The wave of jealousy that surged through me took me by surprise. Mark had had several girlfriends; why wouldn’t he have had sex with at least one of them? Just because I was still a virgin didn’t mean my brother had to be too. The logic was undeniable, so why did the idea hurt so much?

“Have you had real sex yet?” I asked, tentatively.

Mark thought for a moment.

“Well, yes,” he confessed.

He didn’t need to ask me; my whole body reeked of virginity and I had just confessed to have never seen a boy cum.

“Who was it with?” I asked.

“You really want to know?”

Part of me desperately wanted to know. Another part knew that the knowledge might hurt me. Another, much bigger part wanted him not to have had sex with anyone.

“Well, do I know her?”

“Yes.”

Oh, God.

“Is she a friend of mine?”

“No.”

Thanking God for small mercies, I breathed out heavily in relief. The idea that my brother might have fucked one of my close friends would have been unbearable.

“Did she teach you how to touch girls…down there?”

“I suppose so. She likes it almost as much as you do,” he grinned.

“Likes?” I challenged.

“Liked,” Mark corrected himself.

My relief deepened. We lay together for a long time before he eventually sighed and spoke.

“I suppose we’d better get cleaned up. We’d better swap your sheets with mine before Mum seen them,” he said. “If she sees semen stains on your sheets, she will start asking questions big time.”

“What about your sheets?” I asked naively.

Mark laughed hollowly.

“It happens to boys in their sleep,” he smiled, embarrassed. “Haven’t you heard of wet dreams? Boys can’t help having them; Mum won’t think anything’s wrong.”

I wiped the sticky goo off my legs and tummy with a couple of tissues. Mark wiped the end of his floppy cock too, then still with the lights off, we stripped the sheet from my bed. It was indeed very messy. Mark carried it to his room then returned with his own clean sheet.

Then the two of us remade my bed. I had changed my messy panties while he was way.

“I’d better go back to my room,” Mark said when all evidence had been removed or covered.

He kissed me on the lips in a way which felt very different from any kiss he had given me before, as if he was softer, more vulnerable, less an older brother than… I didn’t know what.

“Goodnight Annie. And thanks for…well, just thanks.”

I lay awake for a long time thinking, among other things, just how much I wish he had stayed and held me close the whole night, how very jealous it had made me to think of him doing anything with my friends…

And how very strange it must be to have a boy’s weird, uncontrollable body.

***

Things seemed to move quickly from that night. Or at least, having passed an important watershed, we took them in larger steps.

The next time Mark slipped into bed with me, my period was over, and I wasn’t wearing panties. So, after a few minutes of wonderful fingering, I got the full benefit of feeling the top of his shaft rubbing across my bare, sensitised vulva.

It gave me a small, but very pleasant orgasm but made my brother moan aloud when he started spurting onto the hand towel we had placed underneath our hips.

The clean-up was still messy, but this time I was expecting it and could wash and dry the towel without Mum noticing.

A week later, Mark persuaded me to reach behind with my hand while he fingered me, take his shaft in my fist, and rub it up and down. At first, I was surprised by its firmness, the smoothness of its skin, the weird, rounded end with its tiny lips, and the strange way the skin slipped up and down the ridged pole beneath.

Of course, the awkwardness of this position soon became obvious to us both so, for the first time, we turned over and began to touch each other face to face.

I cannot describe how different it felt, actually looking into the eyes of the boy whose fingers were inside my slit, or toying with my clitoris, or slipping into the entrance to my vagina. Mark could read the strength of my reactions on my face as well as on his fingers, as clearly as I could read the lust and desire in his expression.

As a result, I reached a much stronger, much more intense climax much, much quicker.

And of course, lying alongside Mark with his arm around my shoulders, his lips on mine and his cock in my fist as I clumsily pumped it, was a revelation. The look on his face when I eventually made him cum was both frightening and marvellous, as was the spray of pale slimy fluid that spurted from the tiny lips on his tip then flowed all over my fingers and wrist.

From there, it was a relatively short journey to him licking between my thighs.

I had severe misgivings at first, having always considered those parts of me to be dirty, especially when oozing those strong-smelling fluids, but Mark didn’t seem at all put-off.

It took rather longer before I dared try and perform my first ever blowjob on him, and when I did it was clumsy and humiliating, especially when I made myself gag on his smooth end. But together we persevered and by the third evening, Mark pronounced me both a fast learner and a great cocksucker.

Why this insult made me feel proud remains a mystery.

This new regime continued for several weeks, both of us getting better and better at bringing each other pleasure until the Friday night Mum stayed away overnight at Grandma’s house, and we took the final step to where we are now.

It wasn’t planned, at least not on my part. With the house to ourselves, we had no need to hide or keep silent, so lay spooning downstairs on the sofa, watching a late-night horror movie on Netflix. The curtains were closed, the doors locked, the lights low.

I still wore my short nightie and Mark his boxer shorts; we weren’t as comfortable being naked together as we are now, but we snuggled under the duvet, my bottom in my brother’s groin, his head above mine propped on a cushion.

This time, however, instead of stroking my side, Mark’s hand made a beeline for my breast. Having brought its nipple to erection through my nightdress, his hand plunged between my thighs once again, fingering me with an urgency that was entirely new.

Taken aback, I could do nothing but let him have his way; in truth, I wanted nothing other than this, though the pace of his progression was bewildering. Within minutes I was trembling with my first climax and the pungent fishy smell of a girl’s vaginal juices in full flow filled the air.

From there on, things get a little hazy.

Mark had made me so aroused with his fingers that I offered almost no resistance when he made it plain that he wanted to go much further. And even that small hesitation was nerves rather than reluctance; I had no idea what I was supposed to do and didn’t want to make a fool of myself.

I needn’t have worried; Mark took complete control, rolling me onto my back, mounting me gently and manoeuvring the head of his erect cock between my already tingling outer lips. I gasped, staring up into his handsome face as for the first time in my life, I felt a real male penis working its way up and down my slit, seeking my as-yet unpenetrated entrance.

It took half a dozen tentative thrusts before he found the right place and the right angle, and his smooth head actually began to enter me. My body went stiff, my legs closed on his as if to keep him out, but there was no conviction in my efforts, and he was far too determined to be put off by them.

Mark’s shaft felt simply huge as it began its jerky, back and forth journey into my body. I froze with nerves which must have made his job much harder, but he persevered.

The astonishment of feeling my most intimate place being invaded for the first time was intense. The strange, alien sensation of being filled was beyond anything I had imagined, so bewildering and frightening that I didn’t even think about my hymen until a short, sharp sting shot through my tender insides.

I whimpered aloud as the delicate membrane tried to resist his progress, then gasped in shock as a powerful thrust from my brother's hips drove the smooth rounded head of his cock through the last remnant of resistance my virginity had to offer, and deep into the tight, warm passage beyond.

Marks’ cock felt simply huge as it entered; bigger than I had ever imagined a cock could be; filling me more completely than I had imagined in my sexiest dreams.

I froze again, my legs stiff, my eyes wide and fixed on my brother’s face. But he was gentle and patient, and eventually, with many soft words and even more small, smooth strokes, his cock eventually worked its full length into my trembling body.

Tears filled my eyes and rolled down my cheeks as for the first time in my life, I felt the weight of a boy’s hips on mine, the incredible fullness of an entire erect penis deep in my vagina, and the helpless vulnerability of a girl impaled for the first time.

Mark looked down on me with a worried expression on his face.

“Does it hurt?” he asked in a whisper.

I nodded. “A little.”

“Do you want me to stop?”

I shook my head emphatically; I did not want him to stop.

“Okay, Annie. I’ll try and be gentle.”

I bit my lip again as, slowly and carefully, my brother started moving in and out of my over-tight, completely inexperienced vagina. I had expected and was prepared for pain when my body was penetrated for the first time, but the sensation of being repeatedly stuffed full then released was stranger than I had ever imagined, as was the extraordinary sensitivity of my tightly-stretched entrance as my brother’s shaft was pulled through its grasping lips over and over again.

“Christ you’re tight!” Mark croaked, his face only inches above mine, his hot breath on my cheek. “You feel absolutely amazing!”

Although the gasping thrill of my first vaginal orgasm was several weeks away, the warm feeling that his...