Louis had been born into the de Sade aristocracy alongside the likes of Antoine, Veronica and Dominique de Sade, and was able to spend much of his time with the likes of Noé Archiviste, whom Louis' grandfather had purchased at an auction, and while he disagreed with Noé's position on the beauty of the Blue Moon, the two remained close friends throughout childhood.
(Source: Pandora Hearts Wikia)