In 588 his elder sister Theudelinda was engaged to the king of the Lombards, Authari. The potential marital alliance with the Lombards sparked an invasion by the Bavarains' overlords, the Franks, in 589. Theudelinda and Gundoald both fled to Italy. There Theudelinda married Authari in May, and Gundoald was invested with the duchy of Asti and the hand of a granddaughter of King Wacho in marriage. With her he had two children, Gundpert and Aripert.