Warning: There are seriously huge spoilers from Avengers: Endgame ahead. Major spoilers, if you will.
The ending of Avengers: Endgame is downright tragic as the team loses its founding member. In order to save humanity and finally stop Thanos once and for all, Tony Stark (Robert Downey, Jr.) uses the Infinity Stones to snap Thanos (Josh Brolin) and his army away once and for all. Doing so, Tony is critically injured and eventually dies from these complications. One of the final scenes of the movie is a ceremony by the Stark lakehouse and it’s well attended, with appearances from the Stark family, the Parkers, the Pyms, the royal family of Wakanda, Captain Marvel. There's also a seemingly random teenage boy at Iron Man's funeral.
If you found yourself trying to put a name and a face to the kid was in-between some of Earth’s mightiest heroes, you’re not alone. For a complete blast from the Iron Man past, the kid we see here is Iron Man 3's Harley Keener (Ty Simpkins). In case that still doesn’t jog your memory, Harley is the kid who helped Tony out during Iron Man 3, and then at the end of the movie Tony left him a bunch of cool toys. Remember that, now?
Harley’s appearance at Tony’s funeral is certainly jarring, mostly because we haven’t seen him since Iron Man 3 in 2013, which was six years ago. He has never been mentioned since in any of the Marvel Cinematic Movies, and honestly we all probably would have completely forgotten about him had he not showed up at Tony’s funeral (sorry, Harley! Just calling a spade a spade, and Iron Man 3 was… fine). But now that he’s here, and clearly a bigger part of the MCU than we all realized, now what?
Tony’s always taken on the role of a “father figure,” and Harley just happened to be the first kid to step into the picture for this. The second is, of course, Peter Parker and their bond is incredibly close. At one point, well before Spider-Man came back into the picture, was Harley being set up to actually be the kid Tony fully takes under his wing? It’s entirely possible, but also not likely considering that, once again, no one has discussed Harley’s role in the MCU for the last six years.
Also, now Tony has a kid of his own, Morgan. She has clearly already taken a liking to dad’s suits, as at the beginning of Endgame we see her playing with one of Iron Man’s helmets. If that isn’t setting up for Morgan to take on the Iron Man (or another) mantel one day with the Avengers, I quit.
So with the introduction of Peter and Morgan, that just makes Harley’s re-introduction during Endgame that much more confusing. Sure, it can be said that Harley is the only person from Tony’s past who’s not a bad guy and isn’t dead and/or locked up right now (like Justin Hammer, and it’s a shame that Sam Rockwell has yet to reprise this role again). Maybe Harley’s inclusion was just another way to show that yes, Tony Stark has had a heart all along, since once upon a time he helped a kid get over bullying and his absent dad with a bunch of shiny new scientific toys.