The Duke of Sussex is in the UK this week but will not see his family.
The Prince and Princess of Wales celebrated their daughter's birthday by sharing an adorable new photo.
The Princess of Wales said in March that she'd been diagnosed with cancer following abdominal surgery.
Prince William And Kate Middleton Celebrate Their Wedding Anniversary With A Never-Before-Seen Photo
The Prince and Princess of Wales celebrated 13 years of marriage on Monday.
The palace previously announced the king's cancer diagnosis on February 5.
Louis Arthur Charles was born on April 23, 2018, at St. Mary's Hospital in London.
The Queen was born Elizabeth Alexandra Mary in London on April 21, 1926.
The Prince of Wales stepped out for his first in-person engagement after the Princess of Wales shared her health update on March 22.
"Said he wrote a book," the actor quipped after running into the Duke of Sussex.
The Netflix show ended its six-season run last year.