He was the youngest of the four sons of Theodo of Bavaria and his wife Folchaid and the uncle of Swanachild, the second wife of Charles Martel. At first, he co-reigned with his brothers Theodbert, Theobald, and Tassilo II and then, from around 719, alone. His father divided the principality, after involving his two eldest sons with the reign of the duchy in 715.