https://www.hollywoodreporter.com/heat-vision/avengers-endgame-directors-explain-captain-america-ending-scene-1207742
Since Steve Rogers is a noble man, would he really have gone back in time and essentially broken up a family by reuniting with Peggy?
Does this mean that somehow Steve was actually Peggy's husband all along (as one theory goes)?
Or did he create an alternate reality with his actions? According to the Russos, it’s the latter.
"If you went back to that timeline, between the point where Steve went into the ice [in Captain America: The First Avenger]
yet before Peggy met her husband, Peggy was available," Anthony Russo said.
Holmes noted that some fans have found it creepy that Steve Rogers essentially made Peggy's future relationship with her husband,
as well as their two children, disappear. But as the brothers both assured the audience, "They exist in a different timeline."
ついでにラストの家はペギーの家として内装作られてたわよ