He returned shortly after with the ever-adorable Prince George and Princess Charlotte, who walked into St. Mary's Hospital hand-in-hand with their father to meet their new baby brother.
George was dressed in his school uniform, and Charlotte looked super cute in a floral blue smock dress and navy blue cardigan with black mary jane shoes and white socks.
Can we take a minute to appreciate 2-year-old Charlotte's mini royal wave? The Queen would be so proud!
At a photo call outside of the hospital just seven hours after Kate gave birth, William joked to photographers: "We're very happy but we've now got thrice the worry."
We'd say the royal couple are more than happy to deal with a little worry for a third addition to their gorgeous family. Congratulations once again!