Of course, I don't feel terribly much sympathy for them - they've all lived lives of privilege that I will probably never know, and I don't see why they should be able to continue making even more money from something they did half a century ago.
I wouldn't mind so much, except that in the music world, the idea of a derived work has received such a broad definition by the legal system. I mean, I don't think it unreasonable that the Beatles should continue to receive money for copies of their performance of Hey Jude, but why can't another artist do a cover without having to pay them, 50 years down the track? IP was supposed to aid creative expression, not stifle it!