Why do the Emperors daughters or sisters lose their titles if they marry a commoner?
The structure and size of the Imperial Family changed after WWII. Before that time, there were numerous imperial princes and princesses, many of whom belonged to cadet or collateral branches of the Imperial Family. After the war, the occupying allies wanted to reduce the size of the Imperial Family, partly to limit the amount of money that they would receive from the government. The result was the 1947 Imperial Household Law which narrowed the legal definition of the Imperial Family. Under its terms, only the legitimate descendants of an emperor in the legitimate male line had imperial status. The result was that only the immediate family of Emperor Hirohito (or Showa) and those of his three brothers had imperial status. Everyone else, especially those in the junior, collateral branches of the Imperial Family, would lose their imperial rank and become ordinary tax-paying citizens. Neither they nor their children were part of the Imperial Family anymore. The 1947 Imperial Household law
