Jack Kirby's heirs have been denied an appeal in their ongoing legal quest to gain ownership of the legendary artist's famed creations, according to various sources including the Associated Press.

The 2nd U.S. Circuit Court of Appeals in Manhattan on Thursday affirmed a 2011 lower-court decision that the Kirby family had no claim to characters such as the Fantastic Four, the Hulk and the X-Men. Specifically, the legendary creator's estate was seeking to terminate copyrights of both Marvel and licensees Sony, Fox and Universal.

In a 57-page ruling, the court states that "the district court correctly determined that the works at issue were 'made for hire.'" Later in the document, the circuit judges spell out their perspective of the work-for-hire nature of Kirby's relationship with Marvel, writing, "When Kirby sat down to draw, then, it was not in the hope that Marvel or some other publisher might one day be interested enough in them to buy, but with the expectation, established through their ongoing, mutually beneficial relationship, that Marvel would pay him."

This latest development may not be the end of the line for the Kirby family's legal options. The Hollywood Reporter points out that while the 2011 ruling was upheld, the appeals court also made clear that a New York court has jurisdiction over just two of Kirby's four children (Barbara and Susan), as Lisa and Neal Kirby are California residents, and potentially able to continue the challenge in a separate circuit.

The Kirby family -- represented by Marc Toberoff, who has also led the litigation between Warner Bros. and the estate of Superman co-creators Jerry Siegel and Joe Shuster -- started the copyright reclamation attempt in Sept. 2009, shortly after the news of Disney's acquisition of Marvel for $4 billion. The suit covered works created by Kirby from 1958 to 1963, including many of Marvel's most famous and lucrative characters.