Prince Frederik of Luxembourg, the youngest son of Prince Robert of Luxembourg and Princess Julie of Nassau, died in Paris at age 22 on March 1—a day after Rare Disease Day—of a rare genetic ...

POLG mitochondrial disease is a rare genetic disorder caused by mutations in the POLG gene, which is responsible for maintaining the DNA of mitochondria. This disease severely disrupts the body's ...

Crown Prince Christian's younger siblings, Princess Isabella, 18, and 14-year-old twins, Prince Vincent and Princess Josephine ran the One Mile family race together in Copenhagen/Frederiksberg.

King Frederik and his kids supported a staple on the royal family's annual calendar after Prince Joachim revealed whether his family will ever move back to Denmark from the U.S.

Queen Mary and King Frederik have celebrated their son, 19-year-old Crown Prince Christian, taking the next step in his royal career. The Danish royals shared the news as Christian continues to ...