Tatiana Blatnik was born in Venezuela, though raised in Switzerland and is of Russian Jewish origin. Her biological father, Ladislav Vladimir Blatnik, died when she was 6 and she was raised by her mother Marie Blanche. Her stepfather Attilio Brillembourg is the owner of a New York area financial services company.
Princess Tatiana and her brother, Boris Blatnik (born on 21 February 1978) were both born in Venezuela, and are the natural children of Ladislav Blatnik, born in Slovenia and Marie Blanche Bierlein (born in Munich on 10 December 1954). Her maternal grandparents are Ernst Bierlein, born in Munich on 26 February 1920, and wife (married in Munich on 21 February 1945) Countess Ellinka von Einsiedel, born in Würmegg on 26 July 1922, this last by whom she is a descendant of the Prince Elector William II of Hesse.
Prince Nikolaos's engagement to Tatiana Blatnik, with whom he has been in a long term relationship, was announced on 28 December 2009, by the office of King Constantine in London. Until July 2010, when she resigned to concentrate on her wedding plans, Blatnik had worked in the publicity department as an event planner for fashion designerDiane von Fürstenberg. On her marriage, Tatiana became officially styled in Denmark or by courtesy elsewhere as Princess Nikolaos of Greece and Denmark with the style of Royal Highness.