They were near-identical twins, she and him. Fraternal twins that believed they were one in the same, and enough so to be fully identical, if such a feat were ever possible with twins of the opposite gender. They had branded themselves two halves of the same whole ever since they could think coherently regardless, and, looking at them not even for a long period of time, it was not hard to understand why.

Pale blue eyes, auburn waves, freckles in every little nook and cranny; even their faces held the exact same aristocratic shape from their parents, the same somewhat-condescending features. They had even been of the same height until a startling spurt in puberty for him. When they had been smaller with less unique faces—chubby ones that truly did blend into each other back then—they had been able to swap clothes for many hours without their parents catching on, and sometimes people still did mistake them for each other from certain angles, though their similarities did not pertain solely to appearance.

In almost everything they shared the same tastes, whether it was the people they socialised with, the subjects they enjoyed at school—predominately a shared interest in physics and the extension, quantum physics—or the way they drank their tea; in the end, tastes were simply variables, but the ways in which they explored the tastes, forever shared, were constants.

Of course, they differed in personality too, but such things were minor. Robert was more laid-back than Rosalind, more willing to spend his weekends sleeping in than spend them looking up far-fetched theories of science like she did, though she could be rather lazy at times too. Rosalind was far more stubborn, far more incapable of compromise or acceptance of some things, though she ofttimes recollected that she had been the first to sit down in the bath tub when they were toddlers, whilst Robert had argued with their father over the temperature and the depth of the water.

Back then when they were little and could share such baths frequently without controversy, they had often tried to count the many freckles that adorned their bodies, and often found that they were disappointed with the results.

Disappointed that they did not have freckles in the exact same place, or that they did not have the same number of them, or that some did not have the same pigment. Disappointed that Robert's shoulders were less speckled than Rosalind's, and that her chest was less speckled than his. Disappointed that, in that regard, they were not wholly identical, but really as fraternal as medical science labelled them.

To any other person, it wouldn't have seemed like something to become upset over, not being the exact clone of your twin, but to the Luteces, it was like heartbreak.

They craved for the idea that they were the same not just partially, but entirely, completely. They craved for the thought that they were truly the same person split into different bodies, with the same mindsets, the same drives. As children it had merely been a fantasy of theirs, but as teenagers and adults, the concept had became rooted deep within them.

Perhaps then it was not surprising that, with the onset of puberty at the same exact time, they would eventually share a bond that was more than that of between siblings, but perhaps then again, it was. The strong attraction that came with the awkwardness of it all—mostly Robert waking to an overwhelmingly stiff pressure in his boxers pressed to his poor sister's back in the mornings when they shared a bed—was always mutual, but it had taken them such a long time to act on it, and even when they had acted, they had never been able to figure out properly if it was wrong or right.

They were fourteen then, barely teens, camping in the garden at midnight with a million curiosities pulsating through their equally-matched minds. Rosalind had been the one to act first, boldly unbuttoning her blouse before her twin brother and marvelling in the awe she saw in his eyes as he gazed upon a chest that had developed a lot more since he had last seen it. She had not stopped his hands from reaching out towards her, palms carefully cupping soft breasts, and he had not stopped her own hands from reaching towards him, fingers tracing lines above his groin.

That night they had never gone further than petting, examining each other half-naked and eventually falling asleep with their exposed skin touching, but it had been a ripple effect from that point on. The older they got, the more their sexuality began to affect them, so much so that it then began to actually feel painful, such a longing, such a lust that was so clearly marked as a taboo. They felt an aching in their hearts when they were no longer permitted to share a room, and an aching still when they began to date, and experimented with people that were not themselves.

Robert was more of a catch with the girls of their school than she was with the boys, that more sociable variable in his personality in its full form. She was more inclined to expect people to approach her first and make effort, and as such never had more than two boyfriends throughout their whole secondary education, though two was more than enough for her brother, and the never-ending list of girls he had wooed in their classes left a sour taste in her mouth.

After leaving secondary school they promptly moved onto college, and the attempts at dating mutually stopped, but their feelings never did. Robert saw how Rosalind's classmates treated her differently because of her gender and wished always to intervene, but she never let him. He had always disliked his beloved twin sister being looked down upon for such a silly reason, and could never comprehend why sexism was so prevalent in their society, or why the differing organ between her legs mattered so much to the average male. She, however, dismissed it as she always did: coolly and nonchalantly.

After college they enrolled in university, both studying physics, where they found the sexism ran even deeper. Her professors openly scoffed at her, and she found it had become a custom for her to persuade her brother not to start anything when she would relay her day to him, insults and all. She was capable of defending herself after all, as much as he tried to somehow prove his masculinity in that aspect, attempting to do it for her, but whilst university passed quickly and soon aforementioned insults were mostly a thing of the past, Robert could never shake the memory of that night in the tent from his mind, not even as a twenty-five-year-old man who no longer had to look after his twin sister from time to time, but still so deeply wished to.

The night that he walked into her room of their parents' house to find her packing for an apartment she had recently bought at the other side of the county was the night he thought "to hell with it" and kissed her; the night that his brotherly affection turned into something more, and the night that her own sisterly feelings transformed as well.

It was there, whilst they laid together in her bed shrouded by the darkness of the night with her suitcase still wide open on the floor, that Robert confessed he had bought an apartment in the same area, and that he had no intention to not follow her wherever she went after leaving university. It was there, that they both admitted their feelings towards one another were more than pure familial affections, but a romantic love that would be better suited between a man and a woman of zero relation, a fate that they wished would have been given to them rather than being born as twins.

"But then I would be spitting on all of these years we've spent as twins," he told her as he looked up to the ceiling in the pitch black, previously immaculate attire mussed just as hers was as she laid by his side with her head on his chest, "and I refuse to lie and say that I'm not grateful we were together, even if limited by the bindings of modern society…"

Rosalind remained silent then, simply stroking over his chest, though she agreed wholeheartedly despite the lack of response. It was a shame that they were born as twins, unable to ever publicly express their love for one another, but in the same regard it was fortunate that they had been born so closely together and not separated, perhaps even at other sides of the globe.

Besides, she thought, we can always dream, can't we?

The somehow shared dream they had experienced when they were ten of seeing themselves in mirrors, looking the same yet marginally different, became more of a beacon of hope after their realisations than a goal to aspire to, though it was also motivation.

Motivation to find a universe where they could be together, not cruelly designed as siblings, or at least find a universe where such things were accepted. With that in mind, Robert sold his apartment and moved to hers instead. Perhaps it was cold to say that neither missed their parents or extended family after moving, but the opportunity to have full privacy between themselves in their little apartment as the rest of the world believed they were just close siblings was the best they had come across.

For years, they went through all sorts of tests, prototypes, machines with varieties of purposes, and through plenty of investors, but always their efforts seemed fruitless.

They weren't sure if the lack laid in their intelligence—which they doubted—their drive—which they also doubted—or their funds—which they believed affected them most—but it laid somewhere. Rosalind was the one who had to comfort a frustrated Robert in the end, watching him pace around their kitchen-turned-laboratory, eventually walking over to him and stopping him with her smaller hands on his broader shoulders.

"We will get there some day brother," she tried her best to assure him. "We will find what we are looking for." His disbelief was sad but sincere as he looked back at her and sighed, dejectedly, and it took a many more few years for their results to actually come out with something, but he could have waited for a decade in the end, her as well.

One day, it simply clicked. In the middle of the same kitchen, at approximately four o'clock on a Sunday morning, a rip in the fabric of time and space was created—or rather opened—and the two previously sleepy twins peered into the tear only to find two matching sets of eyes peering back at them.

They spoke of a city and a man, and a child that played a part in all of their destinies. Robert turned his nose up at the strict idea of fatalism, as did his counterpart on the other side, though listened as intently as his sister. These twins were not biologically twins but from separate timelines, a curious situation that the actual twins did not envy.

In the end, the tear was not completely stable and did not last for long, though it was more than enough to satisfy either of them. Rosalind sat down on the couch, not even bothering to fix loose ends of her bun as she reveled in their first major accomplishment, though Robert continued to stand and stare for a while at where the tear had once been.

"I suppose I feel rather sad for them the more I think about it," he started eventually, hands briefly in his pockets as he turned to look down at his sister. "I must imagine they're feeling the same now."

Rosalind glanced up at him with a slight raise of her eyebrow, laying her hands neatly in her lap. "And why do you feel sad, brother?" she could not help asking, bemused at his statements. "They have accomplished so much. Myself, my counterpart, she was able to suspend a city in the air through manipulation of a quantum particle, something still I can scarcely believe I was capable of doing." A swell of pride was in her voice, even as she chuckled. "Though she is, technically, not me but another version, still…" She looked back to him. "Are you sad that they have accomplished much more than us yet they are younger, more free?"

Robert shook his head immediately, and walked over to her just to pause before her. "No, no," he answered her swiftly, rubbing over his chin for a moment, "no, not that. I'm not sad for that."

"Then what?" she pressed, her eyebrow lifting further. "What could you possibly be sad about?"

He knelt before her then, rather abruptly, and she thought he was acting ever so strange as he clasped his hands in hers and held them tightly, looking upon her as though she were cherished, but to him, she was.

"I'm not sad that they accomplished more, or that they're less limited," he told her honestly, squeezing her hands absently. "No… It's much more a… issue of variables." She just tilted her head, waiting for him to continue.

"I'm sad for them because… Well, yes, an issue of variables. Since they were not born as twins, and despite the problems that always hang over us because of the taboo of… being related, and us and our… feelings, they did not… experience as much as we have."

"Experience?" More bemusement. "And whatever do you mean by that, brother?"

"By that, I mean…" Robert leant forward to kiss her nose, then smiled at her, even as she went on looking confused. "… I suppose I'm glad I was born your twin, and I'm sad that they weren't born as twins."

She eyed him. "Why?"

He kissed her again, though softly on the lips this time. "They've only had a few years properly together, haven't they? But with you, and us as twins, I've lived a full lifetime by your side—will live a full lifetime by your side—and I've never regretted a single moment being your twin in this way, and I never will, sister."

"And that is why you're sad for them?"

"And that is why I'm sad for them."

Rosalind leant forward herself to press her forehead to hers, closing her eyes and sighing. Then she opened them again and looked deeply into his identical eyes before kissing him back. "Then now I am sad for them, too."