Prince Frederik, the youngest son of Prince Robert of Luxembourg and Princess Julie of Nassau, has died from POLG Mitochondrial disease, a rare genetic condition.

Frederik, 22, died on March 1 and his father, Prince Robert, announced his death on the POLG Foundation website on Sunday.

"Frederik found the strength and the courage to say goodbye to each of us in turn – his brother, Alexander; his sister, Charlotte; me; his three cousins, Charly, Louis, and Donall; his brother-in-law, Mansour; and finally, his Aunt Charlotte and Uncle Mark. He had already spoken all that was in his heart to his extraordinary mother, who had not left his side in 15 years," his father wrote.

Frederik was the founder of the POLG Foundation Founder and its creative director.