Bermudo III of León

Bermudo III or Vermudo III (c. 1015 – 4 September 1037) was the king of León from 1028 until his death. He was a son of Alfonso V of León by his first wife Elvira Menéndez, and was the last scion of Peter of Cantabria to rule in the Leonese kingdom. Like several of his predecessors, he sometimes carried the imperial title: in 1030 he appears as regni imperii Ueremundo principis; in 1029/1032 as imperator domnus Veremudius in Gallecia; and in 1034 as regni imperii Veremundus rex Legionensis. He was a child when he succeeded his father. In 1034 he was chased from his throne by King Sancho III of Pamplona and forced to take refuge in Galicia. He returned to power, but was defeated and killed fighting against his brother-in-law, Ferdinand of Castile, in the battle of Tamarón.

Source: Wikipedia — https://en.wikipedia.org/wiki/Bermudo_III_of_Le%C3%B3n