Louis the Pious
Born in Casseuil-sur-Garonne, in today's Gironde, France, the second son of Charlemagne, Louis was crowned king of Aquitaine as a child and sent there with regents and a court to rule in order to quiet rebellions which were forming after Charlemagne's defeat by the Moors in Spain.
When Charlemagne's other sons Pepin (810) and Charles (811) died, he was crowned co-emperor with Charlemagne in 813. On his father's death in 814, he inherited the entire Frankish kingdom and all its possessions. He was crowned emperor by Pope Stephen IV in Reims in 816. Louis used Benedict of Aniane, a Septimanian Visigothic nobleman and monastic founder to help him reform the Frankish church. One of Benedict's primary reforms was to ensure that all religious houses in Louis' realm adhered to the Rule of St Benedict, named for its creator, Benedict of Nursia (AD 480-550).
Like most Frankish men Louis, who was the second son of Charlemagne, expected to share his inheritance with his brothers Charles the Younger and Pepin. However, both of them died before he did - Charles in battle and Pepin subsequent to his blinding and confinement after joining in a revolt against his father - and Louis inherited the Frankish empire intact.
Louis laid out plans to divide his empire between his three sons from his first marriage with Ermengarde: Lothar (who received the title of co-emperor), Pippin of Aquitaine and Louis the German. He then remarried with Judith of Bavaria and had a fourth son, Charles the Bald. The redivision of the empire to take Charles into account caused his older sons to revolt in 822. After a settlement, Lothar rebelled again in 830. This pattern continued until Louis' death in 840.
After the Battle of Fontenay (841) and the Oath of Strasbourg, the dispute was only settled with the Treaty of Verdun (843) which split the Frankish realm into three parts, the kernels of later France and Germany.