Catherine's parents, her sister and brother-in-law Pippa and James Matthews and her brother James will also be in attendance.
Britain's Prince Louis christened without Queen
The monarch was due to return to London on Monday ahead of a busy schedule of events including a meeting with U.S. This is not the first time the royal family has commented on the baby prince's knack for snoozing.
"The Duke and Duchess of Sussex have been overwhelmed by all the incredibly kind cards and letters they have received on the occasion of their Wedding, and are so touched that you took the trouble to write as you did".
At her first royal christening, the former "Suits" actress gave a nod to her US roots by wearing an olive-toned design by popular American designer Ralph Lauren.
Meghan Markle wore a custom olive green Ralph Lauren dress with matching suede Manolo Blahnik pumps and hat by Stephen Jones.
It was the first time Meghan has attended a royal family event like this, having become an aunt to Prince George, Princess Charlotte and Prince Louis in May. The Duke of Cambridge wore a classic navy suit with white shirt and blue tie.