Osbeorn Bulax's father governed on what king's behalf?
Osbeorn Bulax: Osbeorn (died c. 1054), given the nickname Bulax, was the son of Siward, Earl of Northumbria (died 1055). Siward, Earl of Northumbria:  From 1033 at the latest Siward was in control of southern Northumbria, that is, present-day Yorkshire, governing as earl on Cnut's behalf.
Cnut