Andor's first few episodes quickly established that Cassian was searching for his sister. The show devoted only a small amount of time to showing his early life on Kenari, with it later revealed that the orphans - part of a group of children fighting for survival on a planet ravaged by the Empire - had been separated when "Kass" was taken from the planet by Maarva.
She did that to save him, but Cassian has quite clearly devoted a lot of his life to tracking his sister down...with no luck. During their final exchange, Maarva tries to discourage him from that mission, insisting that Kerri is gone and he will never find her.
It was around that point poor Cassian ended up in prison on Narkina 5, bringing an underwhelming end to the subplot. During a recent interview with Collider (via SFFGazette.com), Andor showrunner Tony Gilroy said the mystery surrounding Kerri is "to be determined."
"A lot of times people don't trust what people say in the show," he added. "I saw people saying, 'Oh, Luthen’s monologue means something else,' 'This means something else.' Maarva's kinda telling the truth. I'd say TBD, I don't want to close the door on it."
We'd like to see this touched in season two, though with four three-episode arcs devoted to the next four years in Cassian's life, it's tough to say when and where it will happen. As for Diego Luna, he seems far more confident we'll pick up with the Rebel's hunt for his sister.
"I don't think it's ever over. I don't think it's over in Rogue One, because I see that as one thing. It's like the feeling, it's one of those things that kind of follow every decision you make, or never letting [go] anymore, not again. That kind of thing. And I think that's behind the decision of that last mission, that suicide mission in Rogue One."
"That's for her. That's for Maarva, that's for his people, for his community. I love the arc that Tony has built, and the arc ends in Rogue One, not in Season 2. I think it's going to be quite amazing to watch Rogue One after you see Season 2. I think you'll see a different film. For sure, you'll understand the character from a different perspective, and you'll be with him in a different way."
Season 2 of Andor is definitely going to be interesting, and no matter what sort of answers we do or don't get regarding Cassian's sister, that should be an absolute must-watch.
All twelve episodes of Andor are now streaming on Disney+.