Charles d'Anjou, comte de Provence and later King of Sicily was, as mentioned in a previous post, a very significant figure in the early history of the Grimaldi dynasty. In 1266, following a victorious military campaign, he became King of Sicily and dominated southern Italy and the Mediterranean area. He had a history with the Grimaldis of Genoa as Gabriele Grimaldi served him as a naval commander. However, after the conflict between the Hohenstaufen German Emperor Frederick II and Pope Innocent IV led to the Guelf-Ghibelline feud, Charles came into conflict with the Republic of Genoa.
The Ghibellines (who supported the Emperor) were successful in Genoa and expelled the Guelfs (who supported the Pope) and these included the Grimaldi family. Because of their past history it was only natural for the Grimaldis to turn to Charles d'Anjou for help in their time of exile. Charles was, in fact, so grateful to the family that had fought for him so gallantly in the past that he compensated them for their losses in Genoa by giving the Grimaldis Ventimiglia, Menton and Roquebrune. Over the years the Grimaldis had to fight hard to keep this territory but they held it until the late 1800's.
Charles d'Anjou fought in the 7th and 8th Crusades, dabbled in extending his influence into the Latin Empire and conquered Albania before waging war on Genoa. He ran into trouble with a nasty little incident called the Sicilian Vespers (which you may have heard of) and fought a war with Aragon before his death in 1285. He had an extensive and storied career, a small part of which was being a friend in deed when his friends the Grimaldis were in need. Their survival allowed them to continue and, in the near future, take the Ghibelline stronghold on The Rock and claim Monaco as their own. His reign would also not be the last time that the families of Grimaldi and Anjou fought together.