I’m increasingly of the feeling that he will never find his sister. It gave him that “fear of being someone who leaves people behind” that Diego Luna mentions and which is first mentioned in the Rogue One novelisation . S2 might well involve him having to leave Bix behind in some way. It would make him all the more determined not to abandon Jyn in Rogue One by turning away from the mission . In other words, I think Jyn becomes the metaphorical lost sister figure. And I can imagine Dedra and Syril trying to bait Cassian with news of his sister.
S2 is going to be a rough watch emotionally I think . There is certainly visual similarities in the imagery of young Cassian comforting his sister, him rescuing Bix, and Jyn supporting him in their final minutes. For Cassian, having lost his family, he kind of finds his family with Maarva, Clem (parents), Bix and Brasso (friends as close siblings ) and others on Ferrix. Then he finds family in the rebellion. Baze even calls Jyn “ little sister” in R1.
It’s doomed, but I hope he and Bix have a little happiness together before the inevitable heartbreak. (And no I don’t think she is his sister literally, but it is Star Wars )
My dream would be that they have a post RotJ epilogue on the show where his sister living in the NR finds his name on a war memorial. Demonstrating she’s been looking for him all this time as well.Sadly they won’t do it. They said the show runs right into rogue one cassian opening scene which imo probably won’t be as satisfying not seeing the work of cassian and the rebellion pay off. They could still end the main part of the show like that and have a post credits scene. I would personally like some form of commemoration to Cassian and the others like this. Alternatively, perhaps Mon holding a private commemoration service. Some kind of payoff anyway.