When could've Captain America had a kid?

[u/cinamonnballzzzz]

/r/marvelstudios/comments/1x4n3qj/when_couldve_captain_america_had_a_kid/

Sorry if this is a stupid question guys but when could've captain America had a kid? In Avengers Endgame Steve went back to Peggy and I'm guessing that scene is like very fresh, that was the firstish time that they'd seen eachother. In Avengers Encore there was an extended version of that scene where Loki comes and --im guessin-- recruits Steve to help fight against Doom. So am I misinterpreting this scene and Steve and Peggy were actually together for years and had a baby?

[u/mike47gamer]

Didn't he adopt Ian in Dimension Z?