Marvel's Eternals movie introduced Harry Styles' Starfox to the MCU, but didn't explain how he can be both an Eternal and the brother of Thanos.

Summary

• The Eternals movie introduces Starfox as an Eternal and Thanos' brother, but doesn't explain how that's possible. In the comics, they are biological brothers, but the MCU may change this origin story.
• The MCU portrays the Eternals as synthetic beings who cannot reproduce, potentially conflicting with Starfox's status as an Eternal. It's possible the MCU will establish Starfox as Thanos' adopted brother to explain the inconsistency.
• Making Starfox Thanos' adopted brother would also explain their physical differences, like Thanos' purple skin. Until Marvel clarifies their relationship, the exact connection between Starfox, Thanos, and the Eternals in the MCU remains unknown.

Eternals introduced a whole new group to the Marvel Cinematic Universe, as well as the character of Eros aka Starfox (Harry Styles), who is both an Eternal and the brother of Thanos - but Marvel didn't explain how that's possible. In the Eternals movie it's established that the group were created by the Celestial Arishem, but it's not revealed until later in the film that they're synthetic beings who Arishem programmed not to evolve. The question of whether Eternals can reproduce isn't addressed in the MCU movie, though star Salma Hayek did say in an interview her character Ajak, "can't have kids."

Still, Starfox's introduction in the Eternals post-credits scene creates a quandary. When Pip the Troll announces Starfox's arrival on the Eternals' ship, he introduces him as the prince of Titan and the brother of Thanos. Then, when Starfox greets Thena, Makkari and Druig, he calls them, "my fellow Eternals." If Eternals are unable to reproduce and Starfox is an Eternal, it presents the question of how he can be both an Eternal and Thanos' brother. Thankfully, there's an explanation in the comics.

Titan Eternals Can Reproduce In The Marvel Comics

In the Marvel Comics, the Eternals characters A'Lars and Sui-San settled on Titan and attempted to devise a way for Eternals to reproduce together. They eventually figure out a way to do so and have two sons together, Thanos and Starfox. This makes Thanos and Starfox biological brothers within the Marvel Comics, but it's unclear if that relationship is the same in the MCU. Before A'Lars and Sui-San, Eternals in the comics are an alien species that are unable to reproduce among themselves, though they can have children with other species.

The MCU, however, changed the Eternals' origin to synthetic beings, with the implication that that's why they can't reproduce. As such, it's possible the backstory of A'Lars and Sui-San may be changed as well. That said, it has already been established in the MCU that Thanos is the son of A'Lars, as his father is referenced by the Red Skull while on Vormir in Avengers: Infinity War. So, at the very least, the connection between Thanos and A'Lars is part of the MCU, but how Starfox fits in is unknown.

Other Explanations For How Starfox Can Be Thanos' Brother

Of course, it's possible the MCU will establish Starfox is the adopted brother of Thanos, which would allow Thanos to be the biological son of A'Lars while Eros is a member of a species unable to reproduce. This would also mean a change to Thanos and A'Lars' origins, making them members of a race other than Eternals in the MCU. This falls in line with what Eternals director Chloé Zhao said in an interview with Empire, explaining Starfox was an Eternal who was "stationed on Titan" but essentially went rogue. If he was stationed on Titan instead of born there, that indicates he's not the biological son of A'Lars.

Starfox being Thanos' adopted brother also more easily explains the differences in their appearances. While Thanos' purple skin is never really explained in the MCU, it's the result of having Deviant genes in the comics. (Originally, all Titans had purple skin, including Starfox, but that has since been retconned.) Since Thanos isn't likely to return to the MCU, making Starfox his adopted brother instead of his biological sibling would explain why they look different without diving into the Deviant Syndrome. Still, until Marvel officially addresses how Starfox can be Thanos' brother and a member of the Eternals, it remains to be seen what exactly their connection is in the MCU.

Key Release Dates