Prince William and Duchess Catherine have released the first official pictures of their baby son, Prince Louis.

The royal couple - who welcomed their third child into the world on April 23 - were ''very pleased'' to share two new photographs, which were taken by Catherine at Kensington Palace, with the world to mark both the birth of their son and also the third birthday of their daughter Princess Charlotte.

In one photo, Louis appears wide awake in a white outfit as he gazes at something out of shot of the camera, propped up on a cushion and a blanket embroidered with a rose. The picture was taken on April 26, just three days after his birth and also William, 35, and 36-year-old Catherine's seventh wedding anniversary.

And in the second pictures, which was taken on Charlotte's birthday, 2 May, the little princess tenderly cradles her sleeping baby brother as she bends over to kiss his head.

Kensington Palace released the images on their Twitter account and wrote: ''The Duke and Duchess of Cambridge are very pleased to share two photographs of Princess Charlotte and Prince Louis, taken by The Duchess at Kensington Palace.

''The Duke and Duchess would like to thank members of the public for their kind messages following the birth of Prince Louis, and for Princess Charlotte's third birthday.''

The royal couple's oldest child, four-year-old Prince George, doesn't appear in the photos.

Both Louis and Charlotte seem to be wearing hand-me-downs in the photos.

Louis' ribbed knit is identical to the Irulea jumper worn by Charlotte in the first official pictures of her, which were released in May 2015 a few weeks after her birth, while the Princess donned the navy Fair Isle cardigan which was worn by her older brother Prince George in his great-grandmother Queen Elizabeth's 90th birthday portrait in 2016.