Hiro could be facing his big brother Tadashi when "Big Hero 7" premieres on the big screen. 

Back in April during the promo tour of Gillette's themed razor products in South Boston, Marvel's former president and CEO Stan Lee mentioned the development of the film. He said that they will begin working on several new projects after the release of "Ant-Man," including the sequel to "Big Hero 6."  

"After Ant-Man, we're going to start playing around with Doctor Strange, the Black Panther, the Inhumans, and then we have to come back for Guardians of the Galaxy 2, Big Hero 6, The Avengers, Captain America ... I don't even know how they decide what to do next, because every one of them is so exciting and the public is waiting for them," Lee stated. 

Rumors begin to circulate regarding the possible plot of the sequel, including the alleged face-off between protagonist Hiro Hamada and his older brother Tadashi, who is said to return with a different persona. 

At the end of the blockbuster animated film released in 2014, Tadashi was believed to be dead after he was trapped in a building filled with numerous robotic inventions. But according to "Big Hero 7" plot speculations, Tadashi survived the fire, but he will be possessed by a villain and resurface as a vicious character named Sunfire. 

Based on the Marvel comics, Sunfire is a Japanese mutant who has the ability to fire flames by absorbing heat from different sources. He was first mentioned in the Marvel universe by one X-Men member. If true, then will Baymax be able to help his friend Hiro defeat his creator Tadashi in the upcoming film?

Hiro, Tadashi and Baymax will probably return to the big screen sometime in 2017 to early 2018, right after the release of "Guardians of the Galaxy 2."