When Sweden's Prince Oscar made his entrance on the world stage earlier this month, 4-year-old Princess Estelle became a proud big sister - even if, as a source said, "she was a little disappointed that he had his eyes closed all the time and couldn't see the drawings she had made." Of course, this is a big sis with a big future: She is also third-in-line to the nation's throne. New stamps, available in Sweden from March 17, show the young royal front and center with the heir apparent (her mom, Crown Princess Victoria) and Estelle's grandfather, King Carl XVI Gustaf.