Louis Robert Paul Ducruet is the oldest-and only-son of Princess Stephanie of Monaco with Daniel Ducruet. He is the nephew of Prince Albert Alexandre Louis Pierre of Monaco, the present reigning prince of Monaco, thus Mr. Ducruet is 7th in line for the throne. At his birth, he was technically 9th in line for the throne (since this was prior to the succession law change of 2002, his illegitimate cousin Jazmin was in line after her father, technically, and his uncle had not yet ascended the throne).
Louis speaks fluent French, English and Italian, and according to his Facebook at one point, he even claimed to know some Japanese!
Happy 20th Birthday, LouLou!