"Great artists like our dad intentionally build their music to last, but we as the caretakers of such treasures, have an obligation to be vigilant about preserving the integrity of the music so that future generations understand its origins and feel its effect as the artist intended, and to assure that it retains its value," the letter says.

The children go on to say that it was Robin Thicke and Pharrell who issued the initial lawsuit against them "forcing us into court" and that they would have gladly settled out of court if the two artists would have admitted the two songs sounded similar and were willing to come to a deal over the song.

They also say that reports that they're suing Pharrell over "Happy" are "100% false." "We have absolutely no claim whatsoever concerning 'Happy,'" they wrote.