Pepin of Landen
Otto was the son of a "domesticus" named Uro who served in the court of Dagobert I. Otto was raised with Dagobert's son Sigebert III and subsequently acted as Sigebert III's "baiolos" (bailiff?). On the death of Pepin of Landen in 639 or 640, Otto challenged the succession of Grimoald to the mayorship. Otto was eventually murdered by Leuthard II, Duke of Alemannia, at the request of Grimoald.