I hurried up to the room that I was sharing with Matt and went straight into the en-suite bathroom, latching the door behind me. I looked at myself in the mirror. My body was still flushed and glowing, and I was a bit embarrassed to see how hard my nipples still were, poking out inside my bikini top. I slipped my top off, baring my breasts, then pulled down my bikini panties so I was naked. Still looking in the mirror, I touched myself between the legs. My clitoris was still aroused, and I slipped a finger inside me to see how wet I was. Damn, I was soaking and still really horny, but it would be dinner soon: I might have to wait until later to satisfy myself properly. Turning on the shower, I soaped myself all over and turned the temperature as cold as I could bear it, to try and cool myself down. I tried to think of non-sexual things, but my mind kept filling with the image of Abi’s naked body and the way she had made me come.

I heard Matt come into the room while I was drying myself off.

“Just a sec,” I said as I heard him rattle on the bathroom door, and I wrapped the towel around me again before letting him in.

“Cheers, Annie,” he said. “I think I need a shower before dinner too.”

And I bet Sally does as well, I thought, unless she wants to sit there at dinner while Matt’s semen slowly seeps out of her pussy into her knickers. On the other hand, she might quite like that; I know I would.

I heard the shower go on, and I listened to him sloshing around while I dried my hair and pulled on one of my summery dresses. I was just primping myself up when I heard our Mum at the door.

“Are you two ready for dinner?” she said.

“I’m just coming, Mum,” I replied. “Matt’s just finished in the shower – I’ll hurry him up.”

I could hear him having a pee. “I’m just going down to dinner with Mum,” I shouted.

“Ok, I’ll just be a minute,” he said, coming out of the bathroom in his boxer shorts, towelling his hair.

Mum and I went downstairs and met my Dad in the bar, where he was choosing wine for the meal. I saw Abi and Sally just sitting down at their table, and I waved innocently at them. As soon as Matt arrived, we sat down for dinner, and spent the meal swapping stories about what we’d supposedly been doing all afternoon; shopping, swimming, walking…some of it was even true. As I was finishing my pudding, I felt a hand on my shoulder, and Abi leant over.

“Did you all have a good day?” she asked. My Mum started telling her what we’d all been up to, when I glanced sideways and realised that Abi’s dress was gaping open at the top and I had a perfect view inside of her left breast. Oh god, she wasn’t wearing a bra and I could see the whole smooth curve of it, right down to her dark nipple. I knew straight away that she’d done it on purpose: I was the only one getting the benefit of her intimate flash. And that answered one of the questions I’d been asking myself in the shower: had she regretted what we’d down that afternoon and wanted to pretend it had never happened? The answer was obviously not!

She and Sally then disappeared towards the lounge, and I did my best to finish my raspberry torte without my hand shaking. Luckily no-one else seemed to have noticed Abi’s cheeky exposure (though I don’t supposed they’d have mentioned it if they had – it’s not the sort of thing our family would talk about over dinner). By the time we got to the lounge for coffee, Abi and Sally had gone. My mind was all in a bit of a whirl about everything – I wanted to find Abi, but I wasn’t sure if now was the right time. In any case, she was likely to be with Sally, so it would probably be really embarrassing trying to make conversation, knowing what I – we - knew. Argh! Why can’t life be simple?

In the end, I finished my coffee and announced that I was going to walk along the cliffs for a bit before going to bed. I was quite pleased that no-one offered to join me, as I wanted a bit of time to myself. I popped upstairs to put on some more comfortable shoes, and went out the side door of the hotel onto the path that led to the cliffs.

It was cooler now that the sun had gone down, but still warm enough to be pleasant. I ambled slowly along the path, and sat down on a bench looking out over the sea. The waves were breaking gently over the rocks below, and it really was very peaceful. I tried to clear my mind of all complicated thoughts, but not surprisingly they kept filling with images of a sexual nature: Matt fucking Sally; Abi masturbating me. My hand strayed between my legs, pressing against my clit through my skirt. I pulled my skirt up and slipped my hand underneath. I could feel the heat between my thighs. Looking round quickly to make sure there was no-one around, I raised my bum and quickly pulled my panties off, stuffing them into my handbag.

It was lovely, just sitting there on the bench, looking out to sea, my legs apart, gently playing with my pussy. I just let my fingers slip inside and wiggled them about, feeling my juices well up. Flickering over my clitoris, I felt myself tingle all over in that lovely sexy way. I was quite happy just keeping myself on the edge of orgasm, building up to it slowly, but then suddenly I was interrupted by, of all things, a Labrador dog bounding past. Whoops – at least I had time to pull my dress down and wipe my fingers on my dress before the owner walked past. We exchanged a few words before he walked on, but the spell had been broken, and I decided to go back to the hotel. With a bit of luck Matt would be asleep and I could finish myself off in bed.

I couldn’t see Matt or my parents downstairs in the lounge when I came back. I went upstairs to our room, and opened the door quietly. The room was dark, and I could hear steady breathing; all this fresh air must have tired him out – that, or the vigorous exercise he’d been getting all afternoon with Sally.

Not wanting to disturb him, I left the light off, undressed quietly and slipped on my short nightie. I brushed my teeth in the dark in the bathroom, groped my way to my bed, and slid under the single top-sheet. It was so hot that we’d each chucked our duvets onto the floor - I’d much rather have been sleeping in the nude, but with Matt there it wasn’t really an option. It wasn’t that we were particularly embarrassed to be naked when the other one was there, but we’d kind of slipped into the habit of respecting the other’s privacy. So he’d get dressed while I was in the bathroom, and vice versa. I’d happily potter around in my underwear with him there, and he usually wore boxer-shorts which didn’t give much away, but I’d have been a bit embarrassed if he’d seen me wandering around with nothing on at all.

So I lay there quietly, thinking back over the day’s events. Watching Matt fuck Sally had been seriously hot, and what had happened with Abi was even more amazing. I was starting to wonder if I should have let it go as far as it had. Shit, she was old enough to be my mother – literally – but what we’d done had been one of the most sexually arousing experiences I’d ever had. Oh god… should I try to pretend it had never happened? And what was she thinking now, lying in her bed with Sally – freshly-fucked Sally – in the same room? Had she mentioned anything to her daughter? I didn’t think she would have, but who was I to know?

All I knew was that all this thinking about sex was making me horny again. It was time to finish what I’d started earlier. I pressed my finger against my pussy through my nightie, and felt how very wet I was. I carefully pulled my nightie up around my waist under the sheet, parted my legs just enough, and slipped a finger between my labia. Whoo, I was still soaking – my finger just slid in with a little “schlup” noise and I felt a dribble of liquid run down between my thighs.

I steadied my breathing, keeping as quiet as I could, and slid a second finger in, before beginning to move them in and out. Trying to be so quiet made me aware of the other sounds in the room, and suddenly I realised that Matt’s breathing was different too – had he woken up? I paused with my fingers up inside me, and held my breath. As I lay as still as I could, I could hear a rhythmic rustling. He was trying to be quiet, but it was obvious – he was having a wank! I stopped my own diddling to listen to the steady swish of his hand against the sheets. I bet I knew what was in his mind – or rather who! What exactly was he imagining doing to Sally? Was she sucking him off, or was he fucking her from behind on the grass? I raised my head and by the light through the curtains could just make out a steady movement at about waist level.

I’m still not quite sure why I did it – things might have been rather different if I hadn’t – but it just kind of happened.

“Hey Matt,” I whispered, loudly enough for him to hear. “Sally’s, like, pretty hot, isn’t she?”

There was a frantic rustle from my brother’s bed, and a rather cross voice whispered back.

“For fuck’s sake, Annie, why aren’t you asleep?”

“I couldn’t sleep for all your wanking, bro! Keep it down, can’t you?”

“Jesus, Annie, can’t you leave it alone?”

“Hey Matt, don’t let me stop you. And I bet I know what you were thinking about too! Sally looked awesome in that little bikini this afternoon.”

There was a bit of a silence.

“And what if I was?” he answered. “There’s no law against it.”

I giggled.

“No law against wanking, no. And no law against doing other stuff, either.”

“What the fuck are you talking about Annie? Doing what?”

“Fucking, of course. I know what you too were up to this afternoon, off together down by the storeroom.”

“We were just having a chat, for God’s sake.” But his voice gave it away – obviously he knew he was lying, and he was wondering frantically if I was just winding him up, or if I somehow really knew what they had been up to.

This was the point at which I could have admitted I was just winding him up, made some kind of sisterly comment about sticky sheets, and gone to sleep. But I thought of Matt with his erect cock plunging in and out of Sally’s pussy, and I was feeling horny and I just wanted to let him know I was cool about it and that I thought he was a lucky guy.

So I just came out with it.

“I saw you,” I said, “Fucking her. I was in the storeroom, getting a sun-bed, and I looked out of the window, and I just kind of …. saw you.”

“Annie! Oh fuck, how could you...”

I rushed on.

“And I’m sorry but I watched and it was so hot and I masturbated and…”

I tailed off. There was another bit of a silence.

“Did you say you masturbated while you watched us fucking?”

“Erm, yes. I’m sorry, but, well…”

“Wow. Fuck it, Annie. That’s a bit weird. Did you see, like, everything?”

“Well, pretty much. I saw you kissing, then she took her bikini top off, then you kissed her tits, then…”

“Whoa, whoa, whoa – stop it Annie! I get the picture…And you saw all of that?”

“Yeah, and the rest.”

“Christ. You won’t tell Mum or Dad, will you?”

I giggled. Now we were over the confession bit, it was kind of funny, and hot too.

“No, of course not. You’re both old enough. And it’s not as if she wasn’t enjoying it too.”

There was a longer silence. And to my surprise I could hear that whap, whap, whap noise again.

“Jesus, Matt, are you wanking again?”

This time he didn’t stop.

“Thinking about you watching us; it’s kind of hot. What did you do?”

“Christ almighty, what do you think? I just put my hand inside my bikini and rubbed myself. You do know what girls do, don’t you?” I probably sounded a bit cross, but I wasn’t - just a bit surprised at the way the conversation was going. Suddenly I felt as if I was on the defensive.

Whap, whap, whap.

“Did you put your fingers inside yourself?”

“Yes, if you really want to know. Jesus, you’re really getting turned on by this, aren’t you?”

“Well, you started it.”

“You were the one who started wanking.”

“That’s not what it sounded like from over here.”

Whoops! Perhaps I hadn’t been as quiet as I’d thought.

I giggled. “Oh god, I was trying to be quiet.”

“I could hear this squish, squish, squish noise. I couldn’t work out what it was at first, then suddenly I realised. And that was really what got me hard; listening to you, like, doing it.”

Oh my God. I don’t think that’s a good thing somehow. But I still couldn’t help asking him the question: “So are you hard now?”

“Yeah, like a rock. And getting harder.”

I leant over and turned on the light over my bed.

“Let me see.”

Matt turned over so he was facing me, and pulled the sheet off. His boxer shorts were pulled down and for the second time that day I saw his erect cock, rearing up out of his dark mass of pubic hair, thick blood-engorged veins running up it. But this time it was much closer, and I watched as it bounced up and down before my eyes. The bulbous purple head was very shiny, glistening with pre-cum. He grasped it and pumped it once or twice.

My mouth was dry. I swallowed. If it hadn’t belonged to my brother, I’d have wanted it.

Matt smiled. “Fair’s fair, Annie. You have to let me see what you were doing now.”

I couldn’t argue with that. “Ok” I said, and pushed the sheet off. My nightie was still up around my waist, and I lay back and parted my legs. I looked over at my brother, his erect penis in his hand, and with a slurp slipped two fingers up into my sopping wet vaginal passage.

As I moved them slowly in and out, I saw him start to wank, four fingers on the bottom of his cock, his thumb on top, letting me see it. I was starting to breathe more heavily, in time with my thrusting fingers. I parted my legs further to let my fingers go deeper. I was starting to tremble with excitement, and with my other hand I pushed my nightie up higher, arching my back to let it slide right up over my breasts. Once they were exposed, I ran my fingers over my nipples, feeling them rise and stiffen. My pink areolae were dimpled as if with goose-pimples.

“Oh Christ, Annie,” muttered Matt.

“I’m soaking,” I whispered, “come and see.”

Matt swung his legs off the bed and walked across the room, his erect cock sticking up at about 45 degrees, swinging slightly. Quickly I pulled my nightie off over my head, so I was totally naked, before returning my attention to my pussy. He stood by my bed, and gazed at my fingers as they thrust noisily in and out of my sticky hole. I could feel my juices running out and down between my thighs onto the sheet. Matt’s eyes moved between my pussy and my bare tits with their erect pink little nipples, as he began to pump harder on his cock. I was strumming my hand over my clitoris, the fingers of my other hand curling up inside me, finding that sensitive spongy spot, and I knew I was going to come quite soon.

So was Matt, by the way he was pumping harder.

“Let me get some bog-roll,” he grunted. But I didn’t want to see his semen wasted like that.

“No, don’t,” I whispered. “Just stand there, by me…”

“What, on your bed?” he gasped, surprised.

“No, on me, you pillock!” I gasped “Come on my tummy…my tits…please,” I whispered. “I’m close…oh god.”

“Oh fuck, Annie, I’m coming.”

A few more rapid pumps, a final squeeze, and my brother's cock erupted: a great arch of wet ejaculate splashed across my chest, leaving a trail over me and onto the bed. Two more great white loops of spunk hit me, stringing over my pink nipples. I could smell it as it began to ooze slowly down my sides and off my boobs. A few last drops were dripping off Matt’s cock onto the sheets as I finally let myself go. I arched my back as I felt my climax engulf me like a wave. The muscles in my legs stiffened, and my little toes wiggled and curled with the force of it.

“Ah, ah, ah, ah, ah, ah, ah, eeeeee…ohhhhh!"

And I whimpered as I came, shaking and writhing. I looked down at the white streaks of Matt’s thick gooey semen splashed across my naked body. I rubbed my fingers in it where it had scored a bulls-eye on my right nipple, massaging it into my firm but pliant breast. Sitting up, I looked down at the wet patch of juices that...