There's a pretty decent chance you've been hearing the name Kate Kane more lately than you ever have before. With Ruby Rose announced to be playing her in the CW's upcoming Arrow-verse crossover--and potentially in her own spin-off series--Kate and her costumed alter ego have been thrust into the spotlight like never before, leaving more than a few fans blinking in surprise. She's one of the most prominent LGBTQ superheroes in the DC Universe but also one of the most niche, thanks to her slightly confusing, multifaceted origins.
First things first: No, Batwoman is not just a new name for Batgirl, and Kate Kane is not just a new Barbara Gordon. They are two completely different characters who actually don't have a ton to do with one another, save for their Bat-connections and home base in Gotham City. And before you ask, no, there tragically isn't a secret "Batboy" to compliment Batman and balance things out. Robin will just have to do.
The concept of Batwoman actually dates back to the mid-'50s, with a character called Kathy Kane, who, despite the similar name and codename, was actually not Kate Kane, but a totally separate person--kind of. The division between Kathy and Kate Kane gets a bit murky through DC's numerous continuity reboots and realignments, but for the sake of clarity, it's generally just best to consider Kathy and Kate as two different people, even though that's not always technically true.
Kate Kane--the Kate Kane that will be showing up on the CW next season--wasn't introduced until the 2006 series "52," a weekly comic that explored the immediate aftermath of a massive, continuity-altering event called Infinite Crisis. In the wake of the Crisis, the major DC ongoing stories all experienced a one year time skip (called, appropriately, "One Year Later") where heroes like Batman, Superman, and Wonder Woman all took a step back from their duties to refocus and reorient themselves. 52 was the story of what happened with that year-long gap and generally involved elevating C- and D-listers like Booster Gold, allowing new characters to take on classic mantles like The Question, or introducing new faces like Kate.
Let's start with a little Gotham City history. The Kane family was a well respected and highly regarded name in Gotham's upper echelons, related to the Waynes by marriage--Martha, Bruce's mother, was a Kane, making Bruce and Kate cousins. The Kanes made their fortune in Kane Chemicals and were said to own basically whatever parts of Gotham the Waynes hadn't already gotten their hands on. While Kate's father, Jacob, was a high ranking military officer, her mother, Gabi, stayed home to raise both Kate and her twin sister, Beth.
Unfortunately, tragedy disrupted what would have been a normal, upper-class childhood. One night when Kate was just a young girl and Jacob was away on work, Gabi, Kate, and Beth were caught in a hostage crisis at a Gotham restaurant. Despite her father's best efforts to martial the appropriate response, Kate was the only one to make it out alive.
Kate grew up to follow closely in her father's footsteps, attending West Point and rising through the ranks with surprising determination and speed. However, when it was revealed that she had been fostering a secret lesbian relationship with one of her fellow students, she was asked to disavow her sexuality or be expelled. She chose expulsion. Jacob supported her choice, however, and facilitated her return to Gotham, where she could finish out her schooling at a normal college. Kate did her best to stay on track but promptly wound up caught in a directionless spiral of partying and rebellion through most of her late teens and early-20s as she grappled with her identity and her past.
It wasn't until she was forced to use her latent military training to thwart an attempted mugging--a moment that brought her face-to-face with Batman for the first time--that she actually began considering stepping into the vigilante lifestyle. She started relatively small, stealing military gear and tech from her father's collections to go out at night, but was promptly caught. Rather than trying to stop her, however, Jacob intervened to insist Kate travel and receive proper training from his military contacts, sending her on a two-year long journey around the world to learn the skills and discipline that would keep her alive.
Upon her return, Jacob presented Kate with a bat suit he had designed and crafted for her, making her transformation into Batwoman complete. She began her new crime-fighting career by reconnecting with an old flame: Officer Renee Montoya, who she had had a romantic relationship with growing up, and who had recently begun training as a vigilante in her own right under the mentorship of The Question. Together, Batwoman and Montoya (later Batwoman and the new Question) worked to defend Gotham in Batman's absence.
Kate is distinct from the rest of the Batfamily thanks to her military background. She's much more formal in her discipline, making her considerably less reliant on a team than she is on her own skill and training. In some incarnations, her father often acts as her Alfred-style advisor, helping her with developing equipment, maintaining her cover, patching her wounds and so on. However, where Alfred generally tries to ease Bruce away from the crime-fighting life when and if he can, Jacob continually puts pressure on Kate to become the best vigilante she can be, sometimes putting her in danger, or undermining her, in the process. This frequently puts Kate in uncomfortable positions with trying to balance her "work" and personal lives while avoiding disappointing her father.
Kate's relationship with the Batfamily at large is frequently pretty distant, though gaining her fellow vigilante's respect has never been an issue. Prior to the continuity reset of Flashpoint, Kate worked with various heroes both in and outside of Gotham. During the New 52, she was given her first solo ongoing series. Now, in the Rebirth era, she's been brought closer to the Batfamily fold than ever in the ongoing Detective Comics series where she's been tasked by Bruce to help train the next generation of Gotham's crime fighters.
With no other official Bat-people to speak of on the CW, the version of Kate we're likely to see Ruby Rose bring to life on the screen is probably going to borrow from a variety of sources. It's likely that her connection to Bruce will be downplayed--the Kanes will likely not be related to the Waynes in this universe, though there is a (pretty small chance) chance as Bruce Wayne has been mentioned on Arrow. Instead, we'll probably see something more focused on the relationship she shares with her father, her military training, and her on-again-off-again struggles with maintaining healthy romantic and personal relationships. If we're lucky, we'll even get to see Renee Montoya join the mix as well.