He was son of Count Eberhard of Nellenburg and his wife Ida, whose origin and lineage is unknown.

He grew up with five brothers and with the succession secured he started a career in the church and ended up in Trier at some point.

[2] After the murder of Archbishop Conrad of Trier 1 June 1066, the cathedral chapter elected Udo, one of their members, to replace him.

[1] Udo became a leading German voice in the campaign of Pope Alexander II against simony.

Beginning in 1075, he became involved in the campaign against lay investiture being waged by Pope Gregory VII against the Emperor Henry IV.