He was born on 16 June 1937 in Sofia, Bulgaria. He was the son of Tsar Boris III of the Bulgarians and Princess Joan of Italy, a daughter of King Victor Emanuel III of Italy. He became Tsar of the Bulgarians upon the death of his father on 28 August 1943. As he was only six years old, his uncle Prince Cyril of Bulgaria became regent, and was regent until his death in 1945. After that, his paternal uncle by marriage, Duke Albert Eugene of Württemberg became regent. However, he died in 1954, when Tsar Simeon II was seventeen years old. Duke Albert Eugene's son, and Tsar Simeon's first cousin, Duke Ferdinand Eugene, himself then 29 years old, became regent and functioned as such until 16 June 1955, Tsar Simeon II's eighteenth birthday, when he was declared an adult. He has reigned ever since.