Jason Todd

Jason Todd (b. August 18th, 1993) is the second adopted child of Bruce Wayne and Tony Stark, as well as the adopted (half-)brother of their various children.
Jason was originally raised by HYDRA in Siberia to be an asset for them like Rebecca 'Bucky' Barnes, otherwise known as the Winter Soldier, and given his own asset name because of it as Тихо (English: Hush). He had a biological half-sister, Cass, who was raised alongside him until they were six years old, when she was taken away. Jason was then rescued by Batman in December of 2002 after he came after Bucky due to her killing his husband's, Tony Stark's, parents. After Bruce died and was then resurrected by Bucky using a Lazarus Pit, he then returned home with her and Jason, who was subsequently adopted by him and Tony. This made him the second child to be adopted by them, the first being Dick.
Jason was then enrolled at St. Philomena's Preparatory Academy, where he became friends with the younger Barbara Gordon. In February 2008, days after Tony was kidnapped by the Ten Rings, Jason presented as an omega, instead of the alpha that he and everyone else had expected him to be because of HYDRA. Despite this, Jason adjusted to being an omega relatively well. When it was revealed that Dick was pregnant, he even took on the mantle from him of being Robin, making him the second vigilante to bear the name.
It is because of his choice to become Robin that the younger Barbara Gordon decided to become Batgirl after she found out that she was to become an alpha because of a genetic mutation. The two of them later met on the streets in their personas, and it was because of her scent that Jason later realized she was Batgirl and that they were scent matches.