Did Aethelred marry king Alfred's daughter?

Yes, Aethelred, Lord of the Mercians, married Alfred the Great's daughter Aethelflaed, Lady of the Mercians c. 886.

Who was the real Aethelred?

Aethelred was Lord of the Mercians from c. 881 to 911 and a key military leader against the Vikings in England. He was a capable and loyal ally of Alfred the Great (r. 871-899) and also his son-in-law after his marriage to Alfred's daughter, Aethelflaed.

Aethelred, Lord of the Mercians Timeline

Definition

Aethelred ruled as Lord of the Mercians from c. 881 to 911 and was a key military leader in the fight against Viking conquest and settlement in England. To defend Mercia, he allied himself to the powerful Kingdom of Wessex under the leadership of Alfred the Great (r. 871-899) and later married Alfred's daughter, Aethelflaed, to strengthen their alliance.

More about: Aethelred, Lord of the Mercians

Timeline

881 - 911
Reign of Aethelred, Lord of the Mercians.
c. 886
Aethelflaed marries Aethelred, Lord of the of Mercians.
892 - 896
Aethelflaed and Aethelred battle Viking armies in defense of Mercia.
c. 900
Aelfwynn, daughter of Aethelred, Lord of the Mercians and Aethelflaed is born; Aethelflaed's nephew Prince Aethelstan of Wessex comes to live with her at Mercian court.
902
Aethelred, Lord of the Mercians, falls ill; Aethelflaed becomes power in Mercia.
911
Aethelred, Lord of the Mercians, dies; Aethelflaed becomes sole monarch in Mercia, known as Lady of the Mercians.