"First Year School Photos 2019 🇲🇨" Charlene captioned the snaps of the siblings.
In the cute snaps, the twins each pose individually, and then together, with their arms around each other. So sweet!
Royals fans commented on the photos, and sent their well wishes to the family.
"Beautiful," said one fan.
"Beautiful and wishing them a great school year 😍🌷🙏🏻" commented another.
While another follower remark how much Gabriella resembled her grandfather, Prince Rainier.
Princess Charlene caused a stir earlier this year when she was seen giving racing car driver Louis Hamilton a friendly kiss at the Monaco Grand Prix.
The star driver leant over to embrace the former Olympic swimmer, while her husband stood next to her, and the royal couple were later photographed exchanging a frosty look.
Charlene a former Olympic swimmer, met Prince Albert of Monaco at a swimming event in 2007, and the pair were married in 2011.