Athelstan was the son of Ealdorman Ethelfrith or Ethelferth , who held lands in Somerset, Berkshire, and Middlesex. His mother was Ethelgyth, daughter of Ethelwulf. His brothers Elfstan, Ethewald, and Eadric, were Earldormen of Mercia, of Kent and of Wessex, respectively.
The rise of Ethelstan's family begins in the reign of King Edward the Elder, when Ethelfrith, whose family background is presumed to lie in Wessex, was appointed an Ealdorman in southern Mercia. Mercia was then ruled by Edward's sister Ethelflaed and her husband Ethelred. Ethelstan himself was appointed by King Ethelstan as Ealdorman of East Anglia and other lands which had formed part of the eastern part of the Danelaw, in the early 930s. His brother Elfstan became Earldorman of parts of Mercia at about the same time, while Eadric and Ethelwaldwere witnessing charters as Ealdormen by 940.
Ethelstan and his family were supporters of the monastic reforms of St Dunstan which introduced the Benedictine rule to Glastonbury. Both Glastonbury, and Abingdon Abbey, were endowed by Ethelstan.
Ethelstan's wife was named Elfwynn. Her family came from the east Midlands. She was foster-mother of King Edgar of England. Elfwynns's lands would later endow Ramsey Abbey, refounded by Bishop Ethelwold in Winchester, Bishop Oswald of Worcester, and Ethelstan's son Ethelwine (Ailwyn) . Byrhtferth of Ramsey, author of a Life of St Oswald in the early 11th century, devoted considerable space to Ethelstan's family, several of whom were buried at Ramsey. The epithet Half-King comes from Byrhtferth's writings. Several members of the family were buried, or reburied, at Ramsey.
The position of Ethelstan and his brothers in the middle of the 10th century has been compared with a similar dominance of the family of Godwin, Earl of Wessex in the 11th century. It is possible that Ethelstan's withdrawal to Glastonbury may not have been a voluntary one. However, the death of Ethelwald in 962 resulted in the families offices in Wessex passing to their chief rivals, a family of Ealdorman Elfhere. The result of this was that the two families were roughly equal in influence. Elfhere's death in the early 970s did not result in a return of the old dominance of Ethelstan's family.
Other people associated with Ethelstan's family include Ealdorman Byrhtnoth, whose defeat at the Battle of Maldon is, commemorated in verse. (ref 33)