I am having trouble retrieving this information. A duke or king of Burgundy took custody of, I'm pretty sure, Odo and Robert, sons of Robert the Strong. It's possible that it was some later Robertians, but I remember it being two sons. Which King of Burgundy was this?
Robert the Strong had been defending Francia against a joint Breton-Viking raiding party. At some point during the battle, he had removed his armour. At that point, the Vikings launched a surprise attack and Robert was killed in the course of the resulting melee.
As an adult, Odo (or Eudes) would become King of Francia from 888 to 898.