LOS ANGELES—The Walt Disney Company Sept. 24 filed lawsuits in Los Angeles and New York seeking to stop the heirs to Marvel Comics artists and writers from reclaiming rights to characters such as Iron Man, Thor, and Spider-Man, which their relatives helped create. Disney-owned Marvel is aiming to invalidate copyright termination notices served against the entertainment giant by, among others, the younger brother of the late Marvel figurehead Stan Lee and the estate of Steve Ditko, who together created Marvel superheroes Spider-Man, Doctor Strange, and others. The media giant acquired Marvel in 2009. Disney’s Marvel Cinematic Universe is a media franchise centered on a series of superhero films produced by Marvel Studios and based on characters that appear in its comic books. The franchise has made nearly two dozen films, including some of the highest-grossing superhero movies ever, including Marvel Studios’ four Avengers films. The lawsuit filed by Disney targeted …