Complex sentence: The last tsar in nominal power was Simeon II of Bulgaria whose reign ended in 1946; for two thousand years after Julius Caesar's assassination, there was at least one head of state bearing his name.
Split into simpler sentences: The last tsar in nominal power was Simeon II of Bulgaria, whose reign ended in 1946. This means that for two thousand years after Julius Caesar's assassination, there was at least one head of state bearing his name.