At the end of Endgame, Steve returned to the past to put the Infinity Stones back to their proper place in time to maintain the time continuum.
He didn’t return immediately even though he was supposed to.
Instead, he showed up moments later as an old man sitting on a bench.
It appears that Steve chose to stay in the past to be with the love of his life, Peggy Carter.
He decided to live out his life with her and waited for the right moment to appear on that park bench so that he could hand over the Captain America shield to Falcon.
Fans started to struggle to work out the timeline shifts, with some believing Steve created an alternate timeline when he stayed in the past.
Endgame co-writer Christopher Markus confirmed that there is only one timeline.
He also suggested that both young Steve and old Steve were present at Peggy’s funeral in Captain America: Civil War.
In Winter Soldier, fans learned that Peggy had a husband and two children.
It never clarified who Peggy married although fans believed Peggy’s husband was someone else.
It makes it possible that her husband was Steve all along.
Endgame co-writer Stephen McFeely shared with Canada.com and confirmed this, although he admitted it was up to Marvel to acknowledge that line of thinking:
“It depends on what story Marvel wants to tell going forward. I don’t know if Marvel wants to tell any more Captain America stories or if Chris (Evans) is up for it. Do they want to tell an alternate timeline story? Chris and I are partial to the idea that Steve is part of a strange, unique time-loop where he has always been there. The husband that you very purposefully did not see at Peggy’s bedside in Winter Soldier is Chris’ Steve. We have always thought that he was her husband. The movies you have been watching follow a line where he always goes back. To be fair, not everyone agrees with us. I don’t even know if Marvel agrees with us. But that’s what we think.”
Endgame directors Joe and Anthony Russo doesn’t agree with them. They previously confirmed that Steve travelled to an alternate dimension to be with Peggy, and even revealed that Bucky knew about Steve’s plan all along.
This theory makes things more confusing for fans, though, because it suggests that older Steve is not the Steve that this particular team of Avengers knew.
Markus and McFeely states that Steve is not just Peggy’s husband but also the father of her two children.
This version of events make more sense and it ties up Captain America’s fate in a better bow than what the Russo Brothers suggest.
When it comes to time travel, keeping things simple is usually best.
Perhaps it’s for fans to decide exactly how many timelines Marvel is working with.
However, Markus and McFeely also wrote Winter Soldier, so their take is the one fans should probably believe.