But how to phrase it?

"Charlotte."

Knowing where you'd been yesterday, her face changed at the seriousness in your tone. She didn't look worried or shy, instead she looked anticipatory and had this slow sway to her, like a cat spotting a chance to eat.

"Michael, Lucy, Mum and Dad are all out today-" You begin, and eyes become more intense somehow again. You've finished making your morning drink and Charlotte carries her food on a plate with you into the living room area in the open-plan downstairs of your home. "-And I was sort of hoping you would be, too."

She had to guess what you wanted privacy for after getting to see Sara's homelife.

"But instead of asking you to leave," She giggled throatily at this as she ate, and, sitting to accentuate her profile to you, looked half-excitedly, half-expectantly at you sideways, "Do you mind just letting me do it with you still here?"

Another, louder and more appreciative laugh, "You can honestly do whatever you like while it's just us here." While leaning towards him conspiratorially.

Taking her at her word, you stripped your pyjama bottoms free and flung them across the room, your hard cock getting harder as Charlotte eyed your form admiringly until you were back to reclining on the sofa.

So many boundaries were up for grabs, and many had just been shattered completely forever between them. With these doors open, and your practised wanking motion sending shivers up your spine, you let your sister watch as she starts talking, your only possible answers being nods.

In between bites, she probed those now-open doorways:

"Do you like doing it in front of me? Or would it really have been better if I wasn't home?"

"Do you normally watch porn?"

"But right now you're just watching me? I don't mind."

Your pace got faster.

"Did Sara's family let you do naughty things with them?"

"Mum asked me about them, you know. When she found out you were staying the night. I told her they didn't have much privacy with each other and I think she guessed that they're nudists, but you can't tell her about anything else they do." Slightly stern on that last, but Charlotte had an almost perfect record of honesty in your parent's eyes, and something like this would retroactively make a mockery of that reputation.

"Don't slow down. Keep wanking, it's unbelievably rude of you to be doing that, and for me to be letting it happen withour making a fuss."She began clearing her plate and taking your empty cup back to the kitchen area.

On the way she dropped her towel, began making new drinks, then coming to a decision, popped out of the room and back.

The jiggling of her naked, bare, nude bottom as she paraded up the stairs and flitted into her room stunned you and burned the image into your mind. Even her swishing, now starting to dry, hair was mesmerising.

She returned laughing, naked and sashaying down the exposed staircase as you stroked your throbbing dick.

Then your eyes picked out what the source of the cocky smirk she had on was. Not just her confident, flagrant, exhibitionist nudity in front of you, her brother. In addition, she carried two large joints and a lighter rolled in her right hand.

The swing of her hips as she approached the sitting room and picked up a glass to use as an ashtray enchanted you, and her straight legs and round ass as she bent double to grab it made your hips buck into your pounding fist.

Charlotte looked back over her shoulder and shifted, giving you a complete view of her wrinkled asshole and the smooth cheeks surrounding it, and her puffy pink pussy, enclosed in her lips but dripping wet and waxed clean right now.

Plopping back on the sofa next to you, she said: "This is what I do when no one else is home." And she lit one joint, taking a huge drag.

You almost shook your head in dazed bewilderment. She looked so hot right now. Taking the other joint you drank in her naked form and face easily as pretty as Sara's.

"It feels so much better to cum when I'm stoned." She moaned, starting to rub her thigh with one hand, then gathering herself and bringing up the internet on the large tv. "What turns you on to watch?" She asked, swinging her head towards you at the naughty question, clearly relishing the devilishness of wanking with her brother.