What they were doing was wrong. Rosalind knew it her heart. He was her brother and she was his sister and they should not be doing this. His hands pulled her hair out of its careful updo. The sound of the hairpins hitting the floor of their laboratory was drowned out by their moans as they kissed each other. There had been previous incidents. A kiss stolen while studying, a midnight walk or two that had been spent more in temptation than in motion. Mostly they did their best to ignore their urges. Robert had even dated at one point, though Rosalind knew that it had been a short lived and somewhat embarrassing affair for him.
She didn't have the strength to fight her desires anymore. Tonight was a special night and they were going to celebrate it. Her fingers found the buttons of his waistcoat and she began to undo them, impatience making the task monumentally harder. Robert broke the kiss and pulled back enough to undo his own buttons. For a few moments the room was filled only with their paired, frantic breathing. Rosalind unbuttoned her bodice, suddenly desperate for Robert to see at least a little of what she kept hidden under so much clothing.
He shed his waistcoat and began to undo his shirt, apparently possessed by the same desire. They shared everything. They'd shared a womb, shared their parents' attention for so many years, shared toys and stories and homework. They shared the lab space they were working in, and the shared the discovery they'd just made. This was a natural progression of that. Sexuality was so important and they wanted to share that with each other.
Robert moved closer to pull Rosalind out of her clothing. The lights of the lab were harsh and impersonal but even under the less than ideal lighting he felt himself go weak in the knees when he saw her shoulders and chest. She wasn't even truly undressed yet and he couldn't imagine a sight more lovely than her like this. She was blushing and panting but she stripped out of her outermost garments so fast he felt like he might blink and miss it.
Rosalind didn't hesitate to bare herself to him. He was standing there, staring at her slack jawed and that was fine. She felt silly and crazy and wrong but his gaze made her feel hot inside. She knew his hands and mouth could incite such a flame. She hoped he would be able to help her relieve it.
His hands descended on her almost as soon as she had stripped down to her true undergarments. His hands first went to her waist, drawing her tight against his body. When she came in contact with his erect cock they both groaned at the sensation. They kissed with mad passion while he stroked his fingers over her corset, deftly untying the strings. He felt her hands between them. She was undoing his pants and all he could thing about what the anticipation of feeling her sweet body around him.
He broke the kiss and met her eyes. "I've never. . . You'll be my first." He blushed when he said it, but he felt that he should. Rosalind should know what this meant to him, that he had as much stake in it as her.
She nodded, pushing his pants down just enough to free him from their confines. She took the opportunity to shuck him out of his shirts, leaving him exposed from the middle of his hips up. "I know. I wanted you to be. . . We can never do this again."
"Of course not." He said, tugging her chemise off her shoulders. She straightened her arms so it would fall to the bent forward to unclip and remove her stockings, then her shoes. Robert did the same with his pants and footwear, until they were both stripped down to nothing. Rosalind reached out with tentative care, her hands slowly coming to rest on Robert's chest.
Robert returned the motion, his palm resting on the flat plane of her chest just above her breasts. "I'm serious, brother." She said, before her hand trailed down his body, stroking through his body hair. He slipped his hand down to cup her breast and they both moaned softly at the delightful touch they were receiving and the sensation of the other's body. "We can't explore simultaneously and expect to see everything." If they could only ever do this once she wanted to remember it forever.
Robert's hand stilled, then he nodded. "Allow me to go first. I'm afraid if you touch me too much at the moment I will be overcome and be reduced to begging for more."
Rosalind smirked, just a little. Her hand slipped further down his body, cupping around his cock. He gasped, his eyes widening. "New plan. Let's do that instead."
Robert shuddered and had to fight against his normal reactions. Living in a dorm with no privacy had made him quite adept at pleasuring himself quickly. Now he had to focus on remaining calm or he would never be able to have what he'd wanted since he first learned about relations between men and women. "Please let me touch you first." He didn't care if he was reduced to begging so fast. He needed to give her pleasure and to explore her as much as he could.
Rosalind gasped at the raw need in his voice. She thought his expression might well be her undoing. She relaxed her arm, her hand falling to her side. "Yes. Please touch me." She was breathless and blushing but for once he didn't tease her for her eagerness. He spread the shawl she'd brought along with her to ward off the chill in the lab on the floor and gently drew her down to it.
His fingers explored every curve and feature of her body. Her breasts were soft and yielding to his touch. The skin was so smooth and perfect. He bent his head down to taste the skin of her chest, his mouth moving with impatient speed toward her erect and delightful nipples. He teased the near one with his mouth and the far one with his fingers. Rosalind's composure was quickly eroded under the influx of new sensations. She moaned and writhed under his fingers, each new touch and sensation making it harder and harder for her to focus on anything but his hands and the electricity that played across her skin with every touch. Robert had to take a moment to regain his composure after seeing Rosalind's reactions. Just watching her like this was easily the most intense thing he'd ever experienced.
His hand slid down the smooth plane of her waist, his fingers brushing over her belly button. She laughed with delight and also because it tickled. He remembered tickling her when they were children and wondered if he'd ever imagined then that he might still find such delight in it when they were adults. Rosalind pushed his hand downward after a moment. She was in no mood to be tickled. She was too impatient to wait around while he tormented her. "Hurry up." She complained.
The hair between her legs was stiff and wiry, like his own. His fingertips brushed through it and she arched up to his touch, whimpering wantonly. He hissed and took a deep breath, his hands shaking a little. He had never been so hard and desperate in his life, but he had to continue, he had to touch her as she'd touched him, at the very least. His fingers continued their exploration. He'd heard of the idea that women produced a lubricant to aid sexual stimulation, but he'd never really considered that idea in practice. He gasped when he found the moisture between her lips. She was slick and warm and he knew he would soon reach the end of his patience.
Rosalind loved the way his fingers felt. She grabbed his wrist and moved his fingers against her clitoris, mewling softly at the familiar but new sensation. Even if the motions were the same his fingers felt vastly different from her own. He took relatively little coaching to understand what was happening. He moved on his own after a couple strokes, testing each direction he might stroke her. Some were better than others. Rosalind let out a strangled gasp when he stroked her correctly. He was unable to resist moving his fingers down to her vagina. He slid a finger into her, whimpering when he felt how warm and wet it was. "Oh God," he groaned.
"I think we've both endured enough." Rosalind whispered. Robert's head jerked to meet her eyes. He withdrew his hand and moved between her legs. Her hands moved immediately to his shoulders. He struggled for a moment to find a position that wasn't awkward.
The fumbling and uncertainty made Rosalind extremely impatient. She had to fight not to snap at Robert to hurry up. He was as nervous as her, after all, and that didn't seem helpful. Eventually he found an acceptable angle and the impatience of the wait evaporated from both of them. They groaned simultaneously as he slowly pressed inside her. Robert bit his lip to restrain himself from frantically pounding into her. She felt so good around him. The heat and moisture were so intense and delicious he thought he might cry from the sensation. Rosalind gripped his shoulders tightly, their eyes meeting as he started, tentatively, to move inside her.
Rosalind felt full in a way that was both intense and extremely satisfying. His movement inside her was intense and exciting. She closed her eyes and began to whimper as he moved. Each inward thrust seemed to stoke the fire of her pleasure, making her ache for each new thrust. She drew his mouth down to hers to silence their moans.
Robert's patience eroded as Rosalind became more responsive. He groaned and braced himself on his arms, thrusting down into her with all of his might. Rosalind responded immediately to the increase in pace and fervor. The stimulation became too much, her body bucked upward as Robert's thrusts sent her over the edge. She felt each thrust send another all consuming wave of sensation through her. She mewled his name softly at the end of it all, when she relaxed, truly spent for the first time in her life.
Robert was only a second behind her. He was certain that it was the way she said his name that sent him irrevocably over the edge. He buried himself in her, ducking his head down to rest on her shoulder as his entire body spasmed and he felt the sweet darkness and intense overwhelming sensation of his orgasm. He cried out wordlessly as he came, shivering lightly when it ended. He rested on top of her, sighing softly.
Rosalind stroked her hands up his body, hugging him close for a moment. "I love you, Robert." She said it softly, as though there were others around to hear it. Perhaps she thought it might be less true if it was not spoken loudly.
Robert looked up slowly, meeting her eyes. He knew he would not rest until he'd had her again, until he could have her forever. He saw in her eyes that she was thinking the same thing. "I love you too, Rosalind."
They lay there for a few minutes, his cock still buried inside her, even after it had gone limp. Above them, suspended by nothing but its contents was a metal box that shone with a dull, dingy yellow light. The Lutece Particle, as it would come to be called, was the start of something new and exciting for them.