Six-year-old Simeon Hassan Munoz is now a Bulgarian citizen. The decree was issued by Bulgarian Vice President Margarita Popova.
Young Simeon is the only child of Princess Kalina of Bulgaria, 41, and her Spanish husband Kitin Munoz.
Princess Kalina, the only daughter of King Simeon and Queen Margarita, also became a Bulgarian national. She said she wanted to become a Bulgarian because she loves the country and her father, and she would like to be a member of Bulgaria's national equestrian team.
The princess is the youngest of King Simeon's five children. She and her four older brothers were all born in Madrid.
She married Munoz in a traditional ceremony in Bulgaria in October 2002. She gave birth to Simeon Hassan in Bulgaria on March 14, 2007.