Family Further information: House of Wessex family tree Alfred was a son of Æthelwulf, king of Wessex, and his wife Osburh.[3] According to his biographer, Asser, writing in 893, "In the year of our Lord's Incarnation 849 Alfred, King of the Anglo-Saxons", was born at the royal estate called Wantage, in the district known as Berkshire[a] (which is so called from Berroc Wood, where the box tree grows very abundantly)." This date has been accepted by the editors of Asser's biography, Simon Keynes and Michael Lapidge,[4] and by other historians such as David Dumville and Richard Huscroft.[5] However, West Saxon genealogical lists state that Alfred was 23 when he became king in April 871, implying that he was born between April 847 and April 848.[6] This dating is adopted in the biography of Alfred by Alfred Smyth, who regards Asser's biography as fraudulent,[7] an allegation which is rejected by other historians.[8] Richard Abels in his biography discusses both sources but does not decide between them and dates Alfred's birth as 847/849, while Patrick Wormald in his Oxford Dictionary of National Biography article dates it 848/849.[b] Berkshire had been historically disputed between Wessex and Mercia, and as late as 844, a charter showed that it was part of Mercia, but Alfred's birth in the county is evidence that, by the late 840s, control had passed to Wessex.[10] He was the youngest of six children. His eldest brother, Æthelstan, was old enough to be appointed sub-king of Kent in 839, almost 10 years before Alfred was born. He died in the early 850s. Alfred's next three brothers were successively kings of Wessex. Æthelbald (858-860) and Æthelberht (860-865) were also much older than Alfred, but Æthelred (865-871) was only a year or two older. Alfred's only known sister, Æthelswith, married Burgred, king of the midland kingdom of Mercia in 853. Most historians think that Osburh was the mother of all Æthelwulf's children, but some suggest that the older ones were born to an unrecorded first wife. Osburh was descended from the rulers of the Isle of Wight. She was described by Alfred's biographer Asser as "a most religious woman, noble by temperament and noble by birth". She had died by 856 when Æthelwulf married Judith, daughter of Charles the Bald, king of West Francia.[11] In 868, Alfred married Ealhswith, daughter of the Mercian nobleman Æthelred Mucel, ealdorman of the Gaini, and his wife Eadburh, who was of royal Mercian descent.[12][c] Their children were Æthelflæd, who married Æthelred, Lord of the Mercians; Edward the Elder, Alfred's successor as king; Æthelgifu, abbess of Shaftesbury; Ælfthryth, who married Baldwin, count of Flanders; and Æthelweard.[14] Background Map of Britain in 886 Alfred's grandfather, Ecgberht, became king of Wessex in 802, and in the view of the historian Richard Abels, it must have seemed very unlikely to contemporaries that he would establish a lasting dynasty. For 200 years, three families had fought for the West Saxon throne, and no son had followed his father as king. No ancestor of Ecgberht had been a king of Wessex since Ceawlin in the late sixth century, but he was believed to be a paternal descendant of Cerdic, the founder of the West Saxon dynasty.[d] This made Ecgberht an ætheling - a prince eligible for the throne. But after Ecgberht's reign, descent from Cerdic was no longer sufficient to make a man an ætheling. When Ecgberht died in 839, he was succeeded by his son Æthelwulf; all subsequent West Saxon kings were descendants of Ecgberht and Æthelwulf, and were also sons of kings.[17] At the beginning of the ninth century, England was almost wholly under the control of the Anglo-Saxons. Mercia dominated southern England, but its supremacy came to an end in 825 when it was decisively defeated by Ecgberht at the Battle of Ellendun.[18] The two kingdoms became allies, which was important in the resistance to Viking attacks.[19] In 853, King Burgred of Mercia requested West Saxon help to suppress a Welsh rebellion, and Æthelwulf led a West Saxon contingent in a successful joint campaign. In the same year Burgred married Æthelwulf's daughter, Æthelswith.[20] In 825, Ecgberht sent Æthelwulf to invade the Mercian sub-kingdom of Kent, and its sub-king, Baldred, was driven out shortly afterwards. By 830, Essex, Surrey and Sussex had submitted to Ecgberht, and he had appointed Æthelwulf to rule the south-eastern territories as king of Kent.[21] The Vikings ravaged the Isle of Sheppey in 835, and the following year they defeated Ecgberht at Carhampton in Somerset,[22] but in 838 he was victorious over an alliance of Cornishmen and Vikings at the Battle of Hingston Down, reducing Cornwall to the status of a client kingdom.[23] When Æthelwulf succeeded, he appointed his eldest son Æthelstan as sub-king of Kent.[24] Ecgberht and Æthelwulf may not have intended a permanent union between Wessex and Kent because they both appointed sons as sub-kings and charters in Wessex were attested (witnessed) by West Saxon magnates, and Kentish charters were witnessed by the Kentish elite; both kings kept overall control and the sub-kings were not allowed to issue their own coinage.[25] Viking raids increased in the early 840s on both sides of the English Channel, and in 843 Æthelwulf was defeated at Carhampton.[24] In 850, Æthelstan defeated a Danish fleet off Sandwich in the first recorded naval battle in English history.[26] In 851 Æthelwulf and his second son, Æthelbald, defeated the Vikings at the Battle of Aclea and, according to the Anglo-Saxon Chronicle, "there made the greatest slaughter of a heathen raiding-army that we have heard tell of up to this present day, and there took the victory".[27] Æthelwulf died in 858 and was succeeded by his oldest surviving son, Æthelbald, as king of Wessex and by his next oldest son, Æthelberht, as king of Kent. Æthelbald only survived his father by two years and Æthelberht then for the first time united Wessex and Kent into a single kingdom