Æthelred I was King of Wessex from 865 until his death in 871. He was the fourth of five sons of King Æthelwulf of Wessex, four of whom in turn became king. Æthelred succeeded his elder brother Æthelb
Æthelred as depicted in the early fourteenth-century Genealogical Roll of the Kings of England
Charter S 332 dated 863 of King Æthelberht. Æthelred attests second from bottom on the left as "Æthelred fil[ius] reg[is]".
Charter S 338 dated 867. Æthelred, King of the West Saxons and the Men of Kent, grants Wighelm, priest, a seat in St Martin's Church, Canterbury, together with land. Most charters only survive as copies, and this is the only original of Æthelred to survive.
Silver penny of King Æthelberht of Wessex (Æthelred's predecessor)
Æthelhelm or Æþelhelm was the elder of two known sons of Æthelred I, King of Wessex from 865 to 871, and Queen Wulfthryth.
Will of Alfred the Great, AD 873–888, granting land to Æthelhelm (11th-century copy, British Library Stowe MS 944, ff. 29v–33r)