Athelred was the fourth son of King Athelwulf and his wife Osburga. She was the daughter of Oslac, Athelwulf's butler. While his father was in Rome and France, 855-856, his oldest brother Athelstan had died. Prior to his death two years later Athelwulf left a will. in that will the two eldest sons, Ethelbald and Ethelbert should have the kingdom. When Ethelbald died in 860, Ethelbert became the king of Wessex. But their father's will had made no provision for Athelred and Alfred, the two youngest sons, to be kings. Possibly for that reason Ethelbert did not appoint his brother Athelred King of Kent. He consolidated everything into the single kingdom of Wessex. In 865 Vikings raided into Kent and the men of Kent agreed to pay them ransom. But the Vikings the eastern part of Kent despite the pending treaty.