Page "Louis the Pious" Paragraph 5

Louis was one of Charlemagne's three legitimate sons to survive infancy, including his twin brother, Lothair.

According to Frankish custom, Louis had expected to share his inheritance with his brothers, Charles the Younger, King of Neustria, and Pepin, King of Italy.

In the Divisio Regnorum of 806, Charlemagne had slated Charles the Younger as his successor as emperor and chief king, ruling over the Frankish heartland of Neustria and Austrasia, while giving Pepin the Iron Crown of Lombardy, which Charlemagne possessed by conquest.

To Louis's kingdom of Aquitaine, he added Septimania, Provence, and part of Burgundy.