The dispute has become serious enough that Thicke, Pharrell Williams and Clifford Harris Jr.(T.I.) filed a lawsuit in a California federal court on Thursday to insist that Gaye's family does not have interest in the copyright of "Blurred Lines."
This is from the introduction of the lawsuit, via Hollywood Reporter:
"Plaintiffs, who have the utmost respect for and admiration of Marvin Gaye, Funkadelic and their musical legacies, reluctantly file this action in the face of multiple adverse claims from alleged successors in interest to those artists. Defendants continue to insist that plaintiffs' massively successful composition, 'Blurred Lines,' copies 'their' compositions."
It isn't an uncommon thing to happen in music, because so much of it is unoriginal and redone to fit the style's of the day. There's a dispute over whether's is copying or rediscovering and changing. It's an interesting spat, though.