Harald II was a son of Sweyn I Forkbeard; his brother was Canute the Great. Actually very little is known about Harald. He served as regent in Denmark while his father was busy in England. After his father’s death in 1014, Harald became King of Denmark and Canute eventually became King of England, as the brothers divided their father’s lands.
It’s believed that Harald died in 1018 and at that point his brother Canute became King of Denmark as well as King of England.