11th-century Norman nobleman and the uterine half-brother of William the Conqueror
Robert (Rotbert), Count of Mortain (right) sits at the left hand of his half-brother William, Duke of Normandy. Robert's full brother Odo (Odo Ep[iscopu]s, "Bishop Odo") sits to William's right, implying his seniority. This scene in the Bayeux Tapestry occurs near Hastings, immediately before William ordered the building of a castle there, shortly before the Battle of Hastings.