Her Royal Highness Princess Margaret - Her Royal Highness Princess Margaret celebrated her 21st birthday recently at Balmoral Castles in Scotland, where a ball was held in her honour sod bonfires were lit. Princess Margaret was born at Glamis Castle on August 21st, 1930, and was the first Princess it the direct line or succession to be born in Scotland for 300 years. These pictures show Princess Margaret at various ages, ands, in the centre, the latest study of her token just before her 21st birthday. July 17, 1953.