We do have the flashback scene between Kane and Veronica, and iirc, they were also talking about their mother (could be a symbol). There is also the "sense of familiarty" sometimes popping in Kane's head when he deals with her, and their redness/freckles. If Veronica is Callista's daughter, it would also make even more sense that she is so smart, and why she was trusted by her father to supervise the gambit. And because Olivia and her were born at almost the same time, something could have happened, resulting with the daughters raised by another mother.