The Bat-Family is a host to a lot of different people who have come together to form a family, and while almost none of them are actually blood-related, Jason Todd were almost siblings. Cass and Jason rarely interact with one another, aside from a bar fight here and a jump scare there, but they came very close to actually being brother and sister.
Cassandra Cain was raised since birth by her father, David Cain, to be the most deadly fighter on the planet. Cass is an incredible fighter, but she fled from her father when she first killed a man and read his body language, and finally understood what death really was. Eventually, she made her way to Gotham and while trying to help during the No Man's Land storyline, she ended up ing the Bat-Family. Jason Todd grew up in a poor family, his father was a career criminal and his stepmother was a drug addict. His stepmother eventually died from her addictions, leaving Jason to fend for himself on the streets, where he eventually ran into Batman. Despite Jason's terrifying first encounter with Batman, he was recruited to become the Dark Knight's second Robin. From these two backstories, it sounds like they don't have much in common besides having hard lives, but at one they almost had one very important thing in common: a mother.
Cassandra Cain and Jason both wondered for a very long time who their real mothers were. Cass even broke into prison and beating her father near senseless to try and get him to tell him who she was. While David would not reveal the mother's identity, eventually Cassandra found out on her own that her mother was none other than the future Red Hood's mom, it may have been a missed chance on DC's side.
Making Batgirl & Red Hood Siblings Would Be A Great Story Move
While the Bat-Family is made up of found family, Bruce and Damian Wayne are the only two who are actually blood-related. The idea of making the two with the darkest histories actual siblings would have been an interesting and as-of-yet unexplored dynamic for the Bat-Family. One of the few real interactions Jason has had with Cassandra is her first appearance in Rebirth where they fight in a bar in Batman & Robin Eternal #3 by James Tynion IV, Scott Snyder, and Tony S. Daniel. Jason has been friendly with Batgirls in the past but his relationship with Cass has been entirely unexplored, which is unfortunate considering at one point Jason suspected his mother of being the same woman as Cassandra's mother.
If Jason Todd and Cassandra Cain had actually become siblings, they could have ed each other through their most difficult moments in life. Jason has struggled with killing in the past, even recently shooting a man dead in a rage, and Cassandra has also often lacked a system. If Batgirl and Red Hood had been related maybe Cassandra Cain could have helped Jason Todd, and maybe he could have helped her too.
