Athelbald was the second of the five sons of King Athelwulf of Wessex and Osburga. She was the daughter of Oslac, Athelwulf's butler. He was born about 832. He is recording fighting alongside his father in 851 in the battle at Acleah. There the Vikings who had just defeated Berhtwulf of Mercia near London and when they moved into Surrey they were met and defeated by the West Saxons. In 855 his father Athelwulf went on a to Rome. He left the kingdom in the care of Athelbald. After spending a year in Rome and spending time at court of Charles the Bald, King of the West Franks, Athelwulf returned. But he had wed the king's young daughter, Judith. She could not have been any older than thirteen at the time. The Frankish king Charles had insisted that his daughter be queen. When Athelwulf returned to Wessex with his new Queen, Athelbald objected to his father remaining king. To avoid a civil war Athelwulf agreed to take the sub-kingship of Kent. He let Ethelbald retain his position as king of Wessex. Athelwulf died in 858 as the King of Kent. Athelbald then took his father's young wife Judith as his own wife, apparently without a major scandal.