Kate Middleton and Prince William shared a smile during Commonwealth Day services at Westminster Abbey on Monday, March 10.

Middleton wore a Catherine Walker coatdress in a shade of bright red with a twisted bow effect near the neckline. The slim-fitting dress featured circular buttons down the front placket and sharp shoulders with long sleeves and a midi length.

Prince Frederik of Luxembourg died at the age of 22 due to a rare mitochondrial condition called POLG disease— Newsweek has rounded up what you need to know about the illness. The European royal died in Paris on March 1, one day after "rare disease day," according to his father Prince Robert of Luxembourg's public announcement.

Prince Frederik of Luxembourg, the youngest son of Prince Robert of Luxembourg and Princess Julie of Nassau, has died after a lifelong battle with a rare genetic disorder known as POLG mitochondrial disease.

Prince Frederik, the son of Europe's Prince Robert of Luxembourg, has died from a rare genetic disease, his family announced.