There always existed two Steve Rogers (Chris Evans) in the Marvel Cinematic Universe following 2023 Steve’s decision to time travel to the past for a peaceful life with long lost love Peggy Carter (Hayley Atwell), according to Avengers: Endgame screenwriters Christopher Markus and Stephen McFeely.
“Here’s how we reconcile it. We think there have always been two Caps from 1945 to, say, now, and we just didn’t know that. That’s the loop, right?” McFeely told Backstory Magazine when asked if there were consequences or timeline ripples caused by Steve’s fight against his 2012 self or his later decision to retire to the past.
“It’s not Back to the Future rules, it’s branch reality rules. This is not stepping on a butterfly that turns the world into Biff’s casino. You can’t alter your future by going back to the past. We sort of created our own time travel rules wherein, as the Ancient One says, if you remove an Infinity Stone from a timeline, that creates a branch reality.”