Marvel Fan Theory Predicts Robert Downey Jr. as Doctor Doom Could Target Captain America’s Secret Son

If you’ve been paying attention to the most recent Marvel movies, you’ve probably picked up on a strange new trend: the MCU is getting absolutely packed with younger characters and superhero offspring. We’ve now got Franklin Richards (son of Reed and Sue Richards) running around, and even Steve Rogers’ kid has popped up. It’s not exactly subtle—these next-gen heroes are clearly being set up for something big as we roll toward Avengers: Doomsday.

And if you read between the lines (or just browse the right Reddit threads), there’s a growing pile of rumors that all of this is just a meticulously planned prelude to Robert Downey Jr.’s return as a very different Tony Stark… and the MCU’s version of Doctor Doom.

The Doomsday Setup: It’s All About the Kids

According to a pretty convincing bit of fan theory that’s been making the rounds, Doctor Doom’s got his sights set on the MCU’s new wave of superhero children. The theory goes something like this: Doom either kidnaps or straight up kills Steve Rogers’ kid—supposedly as part of some timeline manipulation, or maybe to punish Cap for putting his personal happiness ahead of his Avengers duties. Would Marvel really go that dark? Well, with the stakes ramping up ahead of Secret Wars and another rumored soft reboot, nothing’s off the table.

Here’s a snippet from a fan who pretty much nailed the paranoia and stakes of the current MCU generation:

'Our theory suggests that Doctor Doom will either abduct or kill Rogers’ young one. Why will he do this? It will be either to change the course of the timelines or to punish Steve Rogers for choosing himself above the weight of responsibility.'

So, yes, things could get real messy for Cap and his family.

What We Know About Avengers: Doomsday

• Directors: Anthony Russo, Joe Russo (so, at least the epic scale is in safe hands)
• Writers: Michael Waldron, Stephen McFeely
• Cinematographer: Newton Thomas Sigel
• Studios: Marvel Studios, AGBO
• Release Date: December 18, 2026 (so you’ve got time to catch up)

The Teaser, Theories, and a Lot of Speculation

The first teaser for Doomsday dropped, and of course, online MCU detectives zoomed in on every second. There’s a particularly juicy moment where you see Steve Rogers’ motorcycle and his classic helmet on the tank—which by itself would be 10/10 nostalgia bait—but more interesting is a shot of the glass door at the Rogers Residence. Somebody is on the doorstep. We don’t see Steve walking over, but there’s definitely a figure in the reflection.

Marvel fans being Marvel fans, the consensus is that figure is not Steve. The running theory? That’s Doom himself cruising up to Steve’s house, just like the classic comic moment where Doom strolls into the Baxter Building to pay Franklin Richards a visit.

The speculation machine also has people guessing that Doom’s visit isn’t just for villainy—some are floating the idea that he might try to recruit Cap, maybe even nudge him into the 'Captain Hydra' role. Others think the whole thing is a setup for a major timeline shakeup. The wildest theory? Doom pulls some multiversal shenanigans, Tony Stark comes crashing back from the dead, and then tries to reassemble the OG Avengers.

Looking Beyond: MCU Soft Reboot and Tony's Return?

For anyone not immersed in MCU leaks: the expectation is that Secret Wars will basically reset a big chunk of the universe. Robert Downey Jr. is heavily rumored to show up again as both classic Iron Man and (maybe) alternate-verse versions. So anyone missing his specific brand of snark probably doesn’t have to wait too much longer.

But Is Doom Even a Villain?

Here’s where things get interesting. Ever since a promo image made the rounds online showing Doctor Doom surrounded by the corpses of several Kang variants (gruesome, even by Marvel standards), fans are wondering if Doom is actually doing everyone a huge favor. If he’s cleaning up the timeline to prevent a multiversal collapse, maybe he’s the closest thing the MCU has to a necessary evil—someone who’s willing to cross every line to keep reality from blowing apart. Not great dinner party company, but possibly not 100% the villain of the piece.

So yeah, the next few years of Marvel are shaping up to get weird, complicated, and (if some of these fan theories pan out) really dark for some of your favorite heroes and their families.

Avengers: Doomsday crashes into theaters on December 18, 2026. The speculation is only going to get louder from here, so buckle up.