Honestly, I don't know where I'm going with this. It started with the headcanon that Sabine looked too much like the clones to not be related to one in some way and it turned into this. I have a longer note at the end to explain where I was trying to go.
This is supposed to take place post-fishing scene Star Wars put up on YouTube, pre-Imperial fight scene in the trailer. Like the majority of you, I have not seen the episodes they released at the Celebration so there may be some timeline mistakes when the season actually comes out.
Disclaimer: I don't own anything except the plot
Leaning against the rickety safety railing of the now-stagnant AT-TE walker had seemed like a good idea at the time to Sabine, who had left the crowded interior of the walker to find a breath of fresh she first slipped away the sun had just begun to set over the wide expanse of desert and now, as she picked her way cautiously around the narrow walkway, it sank deeper into the red-tinged horizon.
The stark blue of the sky mixed boldly with the deep red of the sun and Sabine's fingers itched for a can of spray-paint. She recalled the faded emblems that adorned the old clones' armour, as well as the rusted and peeling paint job of the walker, and wondered if they would be willing to surrender their armour and home for some much needed improvements.
Sabine stepped closer to the rail, intent on leaning out to catch the last rays of the sun, but, just as she put her weight on the rusted metal, it gave out under her. The rail crashed into the sand below and, unable to balance herself, Sabine expected to be sent sprawling forward. Just as she tipped over the edge, a hand grabbed the back of her shirt and hauled her up to the walker's platform.
"Watch yourself, kid." Despite being nearly identical, it was easy to identify the clone who had grabbed her through voice alone. "Don't want to explain to your Jedi that another one of his crew nearly died."
Captain Rex steered her away from the gaping hole in the railing to one of the wider sections of the walkway. "Some of this stuff is a little old, a little broken." They stopped walking and Sabine leaned against the sturdy outer-wall of the AT-TE, eyes focused on the red horizon.
"You do know..." He started and rubbed the back of his could see the building awkwardness in him as he continued.
"After travelling the galaxy for this long, it gets pretty easy to recognise a brother's kid." Sabine nodded slowly. It was conversation that she had been waiting for one of the clones to start, once she had taken off her helmet and saw the recognition flash behind their eyes.
Among her new family, Hera was the only one she had told, though she suspected Zeb had figured it out. Kanan and Ezra, for all their Jedi abilities, had been surprisingly unperceptive.
"I never really knew him," it seemed like the easiest place for her to start. "I hadn't even turned two when he died."
Rex nodded and turned to face her directly as he crossed his arms over his chest. Shadows danced on his face as the sun sank farther down behind him.
"Do you know his name?" He waited for half a moment and concerned flashed in his eyes. "Er- if you don't know or-"
"Fives." Sabine cut him off. "He was an ARC trooper named Fives." Rex was quiet for a long time and Sabine was unsure if that was good or bad.
"I knew him," Rex admitted it in a solemn tone, his eyes seemed to have glazed over in what Sabine could only guess to be remorse. The odds were astronomical, she supposed, that out of all the clones she could have met it would be one that had been acquainted with her father.
"He was a good man." Rex shook his head. "A good man, one hell of a trooper and damn good brother."
Sabine could only shrug, unsure of how to respond. "Mom never really talked about him. I think she was mad at him for dying." She didn't elaborate. It was strange enough for her to be talking about her father's death, let alone to a man who easily represented what he could have been.
"He didn't deserve that," Rex tried to assure her and Sabine realised he probably knew much more about her father than she did. "No one deserves to die like that."
"I didn't find about that-" Sabine paused and was unsure how to say it. "Well…I didn't find out about that until a few years ago."
Rex met her gaze and she suddenly felt like the young Imperial cadet searching her father's CT number on a whim. "It was hard finding out he was executed from an old Holonews report."
The old clone shook his head again and Sabine could see the guilt stark on his face. He closed his eyes and rubbed a hand over his grizzled features.
"Fives – your father – he was…" He took a deep breath and started again. "He was the one that uncovered the plot against the Jedi, long before any of us realised it."
The painful memory etched itself into Rex's face, though Sabine could barely comprehend what was being revealed to her. She knew of the Great Jedi Purge and of the clone's instrumental role in it, but she realised what the old man was going to tell her went much deeper than she had previously thought.
"We – clones that is – we were created with organic chips in our brains." Rex tapped the scar on his forehead that Sabine realised the three clones shared. "Fives found out what they were for. To keep us compliant, to make us obey, even to the point of killing our leaders."
"They killed him for that?" Sabine could barely comprehend what Rex was telling her.
"It was the Empire's best kept secret, even before there was an Empire." The sun was almost gone from the sky and Rex motioned for her to follow him back around the walkway, toward the light of the walker's interior where both of their families were waiting.
Though she could still barely understand the old clone's revelations, as she followed Rex back inside, the partial knowledge he had given her made her feel more connected to her father than ever before.
This was more for my own amusement than anything else. From the first character reveal of Sabine, I realised she has a similar eye colour and skin tone to that of the clones and my brain fired off the crazy thought that she might be some rogue clone's kid. When the season two reveal came out and I saw the stylised five on her new armour, I had to get this writing itch out (though I realise the 'five' is from her being 'Spectre Five,' and it's more of a visual throw-back than anything plot substantial).
There might be more to this, there might not. But I do hope you enjoyed it.