Welf originated from a distinguished dynasty of Franconian nobles.

He is mentioned only once: on the occasion of the wedding of his daughter Judith to Emperor Louis the Pious in 819 at Aachen.

His son Conrad later appeared as a dux (duke) in Alamannia and achieved a powerful position in the Upper Swabian estates he possibly had inherited from his mother Hedwig.

His family became politically powerful when Louis the Pious chose Welf's oldest daughter as his second wife upon the death of his consort Ermengarde of Hesbaye.

Though Welf himself never became publicly prominent, his family became interwoven with the Carolingian dynasty.