I don’t know that they’ve had anything to say.
I don’t mean to derail discussion of the funding scandal. Just pointing out that there were multiple parties in the creation of these licensed characters.
And work for hire could still be appealed for creator ownership after a period of years. Jack fought Marvel for his artwork back for a lengthy period (when pages were being sold off at auction I believe to profit the company starting in the 1980s).
And I think Kirby and Simon fought for ownership of Captain America and won (they may have then sold or licensed the chacters back to Marvel).
Don’t recall Ditko’s name ever coming up (he’s a private person).
And the media seems only to willing to gloss over the contributions of others in their mythmaking.
If Lee pursued sole ownership of the trademarked characters with no consideration given to (or waived by) the artists, then it is an incomplete claim of ownership and should not have much support in court. Kirby did not draw the Spider-man comic but he did co-create the character.