It turns out Peter Parker has been in the MCU since 2010's Iron Man 2!
If you recall, there's a scene in Iron Man 2 (watch below) featuring a little kid in an Iron Man mask coming upon a drone in which the real Iron Man arrives to save the kid. "Nice work, kid," Iron Man says.
Many fans have been stating that the kid is really Peter Parker, who goes on to become Spider-Man and gets inspired by Iron Man to be a superhero.
Tom Holland confirms with HuffPost that the kid is indeed Peter Parker!
"I can confirm that is Peter Parker. I can confirm that as of today. I literally had a conversation with Kevin Feige only 20 minutes ago. Maybe I’ve just done a big, old spoiler, but it’s out there now. It’s cool. I like the idea that Peter Parker has been in the universe since the beginning."
So it turns out Peter Parker and Tony Stark have known each other a little longer than Captain America: Civil War!
"Spider-Man: Homecoming" has a July 7, 2017 release directed by Jon Watts starring Tom Holland, Zendaya, Michael Keaton, Donald Glover, Jacob Batalon, Laura Harrier, Tony Revolori, Tyne Daly, Bokeem Woodbine, with Marisa Tomei, and Robert Downey Jr.
A young Peter Parker/Spider-Man (Tom Holland), who made his sensational debut in Captain America: Civil War, begins to navigate his newfound identity as the web-slinging super hero in Spider-Man: Homecoming. Thrilled by his experience with the Avengers, Peter returns home, where he lives with his Aunt May (Marisa Tomei), under the watchful eye of his new mentor Tony Stark (Robert Downey, Jr.). Peter tries to fall back into his normal daily routine – distracted by thoughts of proving himself to be more than just your friendly neighborhood Spider-Man – but when the Vulture (Michael Keaton) emerges as a new villain, everything that Peter holds most important will be threatened.