I'm glad I wrote the almost all of this at night, while I was almost completely out of it from lack of sleep and before my British middle-class prudishness could kick in. First 'real' smut so be kind!
"Lie back," Cesare commands gently.
Lucrezia's brow furrows at the glint in his eye, like he knew something she didn't. Now the final barrier between them had been crossed, there was surely nothing they did not know about each other. How it should be, Lucrezia thinks. His body is covered in a light sheen of sweat, every inch of it now committed to her memory—along with the feel of his lips on her mouth, on her, breasts, on her skin. She thinks she should feel some guilt, as though there were some indelible black mark tainting her soul now they have sinned so greatly. But there is no feeling of regret, only satisfaction more potent than any she had felt before.
"Lie back, Lucrezia," he repeats, lightly biting the shell of her ear. She obeys this time and her hair fans out into his pillows. Cesare smiles over her for a few seconds and Lucrezia absently considers how she must look to him now: his own sister, naked and glowing from their love-making, curling her fingers into his bed sheets like she is his wife on their wedding night (as she said earlier, in a way, this is their wedding night.) Lucrezia smiles back, a coy half-smile that barely turns up one corner of her mouth, and pulls him down by the back of his neck to her lips again. She is sure nothing will ever feel as good as his lips on hers, kissing like passionate lovers rather than siblings, a sin too sweet to deny.
He breaks the kiss first and leans at her side, snaking a hand down her body to the apex of her thighs. Her hips jerk upwards when his finger pushes into her and traces circles around the little area inside her cunt that previously only her own fingers had known. She lets out a surprised little gasp at how good it feels. Cesare smirks, kissing the column of her throat and up to her jaw bone. The rough pad of his finger speeds up when he finds the spot that makes her mouth let out the loudest moan and her body twist of its own accord and he doesn't stop. Lucrezia curses and blasphemes without restraint, and Cesare peppers kisses on her dirty lips like he loves her vulgarity.
Soon (too soon) heat pools in the bottom of her stomach and makes her tense up all over. "Let go," Cesare breathes and she does, reaching up both hands to squeeze her stiff, sore nipples. Her pelvis rises and her thighs close tightly around his hand in her cunt while she cries out her peak but he does not stop, drawing it out as long as he can for her. After it ends, Lucrezia smiles, soft and utterly satisfied. She leans up to brush her lips against his again.
"I shall never love a husband as I love you, Cesare," she reminds him quietly, sincerely.
He holds her face in one hand, his sharp eyes taking in every detail of her face before he smiles as if to say, I know. Cesare lies down, pulling her closer to him so her head leans on his chest and he can wrap his arms around her and pull the blankets up around them. She has no idea what will happen when they see each other in the cold light of day, and she knows that, in this respect, she cannot be his wife. She will have to leave before the dawn, or else risk a servant finding them in this compromising position that went beyond the pale even for their affectionate, tactile relationship. The Rubicon now well and truly crossed, God only knew how they would adapt to the ripple it would create.
Lucrezia had thought he'd fallen asleep, but Cesare's hand blindly pulls the blankets up further to cover her bare shoulder against the cool of the room—a reassuringly familiar gesture of affection. She lay in the arms of her brother, and drifts peacefully to sleep.