During the latest Big Monkey Podcast, Devon makes a point about Starman Jack Knight and says the idea of legacy heroes didn't really exist before Starman. I threw out the name "Union Jack," but didn't have a chance to finish the thought.
Union Jack was originally James Montgomery(created in 1976), who first donned the guise in World War I. He returned to duty in World War II, after his daughter, Jacqueline, was attacked by Baron Blood, James' brother, John. Jacqueline, injured in the fight, receives a blood transfusion from the android Human Torch and, developing super speed, becomes Spitfire. James has a boulder thrown on his legs by the vampiric Baron and has to retire. The mantle is taken over by his son, Brian(the guy standing next to Spitfire).
Years later(1980 in our time), after Captain America is revived from the ice, James finally helps end Baron Blood with the help of Cap and Joey Chapman, who dons the suit of Union Jack, after Jacqueline's son Kenneth declines to take over the mantle.
Before Rick Tyler, Beth Chapel, & Yolanda Montez, before Wally West & Jack Knight, Marvel gave you a superhero legacy.