Monaco’s royal family is clearly not enjoying the coverage of the “Battle Royal” brawl that landed Pierre Casiraghi (Grace Kelly’s princely grandson) in the hospital with a broken jaw. We’re told that lawyers for the royals are firing off legal letters to media in France and Germany who picked up The Post’s exclusive story on the Feb 12 brawl at Meatpacking club Double Seven. Amazingly, they claim the fight is a “private matter” despite businessman Adam Hock’s arrest and court proceedings. Hock has rejected a plea deal, with lawyer Joseph Tacopina insisting his client was the victim and alleging Casiraghi and crew including Stavros Niarchos were “habitual bar brawlers.” They’re back in court May 23.