The little princess, who attends Wilcocks Nursery School, looked sweet in a blue floral dress with a blue cardigan, while George looked dapper in his Thomas Battersea school uniform.
Bookmakers have reported a surge in bets on the name Arthur for the royal baby, who is fifth in line to the throne. The boy is also the Queen and the Duke of Edinburgh's sixth great-grandchild.
Kensington Palace announced that the baby was born at 11am, after Kate was taken by car before 6am to the private Lindo Wing of St Mary's Hospital in Paddington.
To see the adorable pictures of the new prince, see here.
