...y'know, it's not just the fact that Caitlyn knows Viktor, but the fact that this Caitlyn met this Viktor
I know I already talked about this, but like- HELLO??!
Mind you, Caitlyn isn't just a little sister to Jayce, her parents are also Jayce's patrons and her mother works with Heimerdinger (who Viktor used to work for) on the Council- the Council that basically dictated what kind of use hextech was going to serve in Piltover for however long the timeskip was (as said by Jayce in 1x04), so there's no way these two didn't have at least a couple interactions once Viktor becomes Jayce's partner.
Tell you what, I think these two vibed pretty well too.
First thing first, I just know Caitlyn treated the idea of meeting Viktor the exact same way a younger sibling wants to meet their older sibling's crush; "yeah I need to meet this so-deemed super cool person so I can shit-talk about you to them 'cause it's fun, but also what makes them so special to you and/or so stupid they'd want to spend time with you, allegedly?" type of deal. And there's more to this too 'cause- no wait, I really need to stress this point:
I think it's safe to assume Caitlyn didn't have many friends growing up, if any at all, and Jayce (who's what, twice her age?) is seemingly the only person she shared a bond with where she didn't have to pretend to be someone she didn't feel she was, which only became more and more a thing as time went by.
And everything is fine until the events of 1x02: there's an explosion, Jayce is put away, there's a trial and all of the sudden she's lost her big brother under no explanation other than "he's a misfit and you can't be friends with him anymore", and as far as she knows, Jayce will no longer be in her life and will likely give up all his hard work. She lost her best friend and he lost his purpose in life, all in the span of a single day.
...and then, the very next day, everything seems to be fine again? There's a Council meeting, she's allowed to be cool with Jayce again and when she asks what the fuck happened to this man he opens with "So there's this guy...".
I can only imagine little Caitlyn's thoughts whilst she was processing all the new info: "Okay so you're telling me there's a guy with a funny accent, Piltover's most important person's ex assistant, who I nor anyone's ever heard of nor seen for some forsaken reason, who you met literally last night and he sweet talked you into not giving up because it didn't work when I tried- rude but okay- and then he convinced you to commit a crime to help you complete the research my parents funded? When you were already at risk of exile? And that research was super personal to you specifically, but now it's a you guys' thing? And he's from the- WAIT, HE'S FROM THE UNDERCITY?!!"
'Cause Caitlyn was curious about the undercity as a kid too, innocently so; you're telling her she has the opportunity to talk with someone who didn't just go there, but used to live there? Someone who managed to get where he is with nothing other than the sheer power of will?!
Meeting this Viktor guy is no longer just a little "I wish", it becomes a fucking mission.
...meanwhile Viktor's barely aware the Kirammans have a daughter to begin with.
I mean- he does know, but just because Jayce mentioned her a couple times, perhaps forgetting to mention her being a 14 year-old.
Not that Viktor would give a shit either way, he isn't really fond of anyone in Piltover (aside from Jayce, Heimerdinger and Sky) and the likely spoiled heir of an ultra-rich family is no exception to this, regardless of age. However, she is close to Jayce, and her extremely important family is funding what is also his research now, so he's like "whatever, I guess I'll be as cordial as I can with this miss Caitlyn if I ever meet her".
Which happened, at a certain point in time.
I think Viktor was pleasantly surprised to find out that this good hearted and fairly smart girl was also very curious to know more about the undercity- perhaps he's taken a little aback at first; she is a councilor's daughter and he has to pay attention to what he says around her after all. But at the same time, she is a councilor's daughter and if she's so well intended then why not answer truthfully to her questions when she could, one day, help through her family's influence?
And on the other side, little Caitlyn absolutely adores Viktor, and not just because he's witty and has a funny accent, but because Viktor talks to her like she's an adult.
Cait isn't really used to this sort of treatment, but of course Viktor doesn't address her like a clueless child that needs protection from the real word: that's a privilege the kids in Zaun aren't really given, and they are no less important than her. Besides, what's the harm?
It's also great because whenever the Kirammans organize a ceremony of sorts to celebrate some new hextech achievement as Jayce's patrons, Caitlyn and Viktor would manage to chat separately from the rest of the obnoxiously rich guests, so she doesn't have to feel out of place or babied and he doesn't have to be at the centre of attention as Jayce's partner. Viktor would also get a healthy dose of rich people gossip through little Cait's unintentional open disdain for the environment her parents keep her in, and the only reason why Caitlyn allows herself to lower her guard when talking about it is because she knows damn well that Viktor both probably agrees and has no intention nor reason to tell anyone. If anything, he just comments sarcastically to most stories, and she's happy she can share them with someone who won't say "now now, don't say that about so and so".
And of course, whenever Caitlyn comes to visit them in the lab (not a very common occurrence since the 1x01 accident), Jayce is just happy to see them getting along... whenever Caitlyn isn't whispering something to Viktor while they both look at him, at least.
