Bucky Barnes

Bucky Barnes (legal name: Rebecca Permelia Barnes), otherwise known by her persona of the Winter Soldier, is the wife of Steve Rogers and a former HYDRA asset. Born on March 10th, 1917, in Brooklyn, New York, United States, she and Steve were childhood friends. After she presented as an alpha and he an omega, they got married in 1934, when he was sixteen.
Bucky eventually went to go off to fight in WW2, leaving Steve behind, although he later joined the fight after becoming Captain America. While they were separated during the war, she was captured by HYDRA and injected with a knockoff version of the same serum that had given Steve his powers, although she was later rescued by him and the Howling Commandos. She later became friends with Howard Stark and Peggy Carter through Steve, although she had a dislike for Howard due to his obsession with Steve.
Because of her legendary fall from the train, Bucky was assumed to have died. In reality, however, she was recaptured by Hydra and brainwashed into becoming their asset, and was given the name the Winter Soldier by them. She would remain under their hold for decades, and would kill many people including Howard, his wife Maria Stark, and Ana Jarvis, which caused Bruce Wayne to go after her as the Batman to get justice for his husband's family. However, when he found her and Jason Todd being held captive in the HYDRA base in Siberia, he decided to rescue them at the cost of his own life. Bucky later resurrected him using the nearby Lazarus Pit, with the result that he took them back to the Glass House in Gotham.
Although she and Tony did not initially get along, Bucky eventually became an honorary member of his and Bruce's family, alongside members like Selina Kyle, who she met as the Winter Soldier when Selina was still in the Red Room. Despite this, it is likely that they are biologically the same age, although it is hard to say for sure.