Aethelred the Unready
Aethelred the Unready was King of England from 978 to 1016 (and was thus on the English throne at the time of the Wyvern Massacre).
On April 5, 1002, Aethelred married Emma of Normandy (the sister of Princess Elena and aunt of Princess Katharine).
Real-World History
Aethelred (or Ethelred) became King of England after his mother, Elfrida, murdered Aethelred's older half-brother Edward at Corfe, Dorset, in 978. Aethelred was only a boy at the time, around ten years old, and became notorious as one of England's most inept kings. When the Vikings repeatedly threatened to invade England, Aethelred offered them sums of money (called Danegeld) if they'd promise to leave; the Vikings agreed, but soon realized that all they had to do when they wanted more money was to threaten to invade England, and Aethelred would pay them off with more Danegeld.
Increasingly desperate, Aethelred, unable to fight the Vikings (the Anglo-Saxon Chronicle, a contemporary historical record, reported that Aethelred's army always seemed to be at the opposite end of England from wherever the Vikings landed), turned on their relatives who had settled in England and in 1002, ordered that every Dane in England be put to death. Among the victims of the massacre was the Lady Gunnhilda, the sister of King Sven Fork-beard of Denmark; her death encouraged Sven to launch an even more serious invasion of England. Aethelred was at last deposed and forced into exile in Normandy. He returned briefly in early 1016, but died soon afterwards, and his older son, Edmund Ironside, succeeded him briefly to the throne.
Aethelred was married twice. His first wife, Elfleda, bore him Edmund Ironside. His seocnd wife, Emma of Normandy, bore him Edward the Confessor, who would later rule as King of England from 1042 to 1066.
Aethelred's nickname, "the Unready", was actually based on an Anglo-Saxon word meaning "ill-counselled"; it mocked his name, which meant "noble counsel" in Old English.