Nikolaos was born at Casa di Cura Privata Nuova Villa Claudia in Rome, Italy, on October 1, 1969.

[1] The engagement of Nikolaos to Tatiana Ellinka Blatnik, with whom he had been in a long-term relationship, was announced on 28 December 2009 by the office of King Constantine in London.

[4] Until July 2010, when she resigned to concentrate on her wedding plans, Blatnik had worked as an event planner in the publicity department for fashion designer Diane von Fürstenberg.

[10] The Greek Orthodox wedding was held on 7 February 2025 at the Holy Church of Saint Nicholas Ragavas in Plaka, Athens in a ceremony conducted by His Eminence Amphilochios, Metropolitan Bishop of Kissamos and Selino.

[11][12] Οn 20 December 2024, Nikolaos along with other members of the former royal family acquired Greek citizenship, under the surname de Grèce.