Aethelhere was a younger son of Prince Eni, a brother of King Redwald of East Anglia and possibly one-time monarch himself. He married Princes Hereswith, grand-niece of King Edwin of Deira, whom he may have known when he was a boy; since Edwin and his family were exiled to the East Anglian Court. The two had at least three children: the future Kings, Aeldwulf and Aelfwold, and the martyr, St. Jurmin. Having seen the devastation caused to his country through resisting the armies of King Penda of Mercia, in AD 654 - upon succeeding his brother, King Anna - Aethelhere decided it prudent to submit to Mercian overlordship. This was not such a good personal move, since it led him to fight for Penda against King Oswiu of Northumbria at the battle of the River Winwaed the following year. He was killed during the onslaught. He was succeeded by his brother, Aethelwold.