Walt Disney Co. may not end up with full ownership of many of Marvel Entertainment‘s most famous super-heroes if new copyright claims by the children of the late artist Jack Kirby prove successful.

The four children of Kirby, who co-created a number of Marvel’s best-known super-heroes, including the X-Men, Fantastic Four, Thor and the Hulk, have served so-called notices of copyright termination for 45 characters to Marvel Entertainment, Disney (which recently agreed to buy Marvel for $4 billion), Sony Pictures (which owns movie rights to Spider-Man), 20th Century Fox (owner of movie rights to the Fantastic Four and X-Men), Paramount Pictures (which has a film distribution deal for four upcoming Marvel-produced films) and Universal Pictures (which has distribution rights to Hulk movies).

The filings came just a week after Disney unveiled its $4-billion agreement to purchase Marvel but were in the works before that deal was announced.

Source: Los Angeles Times