Instead, he'll be attending the wedding of his ex-girlfriend and longtime friend, Jecca Craig, who is saying "I Do" to Jonathan Baillie at her family's Lewa Wildlife Conservancy in Isiolo, Kenya, on Saturday, a source confirmed to ET.
Once William returns home to his family, he'll have another exciting moment to celebrate -- Queen Elizabeth's 90th birthday!
The Queen rings in her milestone birthday on April 21, and in her honor, the royal family has been sharing their fondest memories of her, including an adorable nickname invented by Prince George.
"George is only 2½ and he calls her 'Gan-Gan,'" the Duchess revealed in ITV's Our Queen at Ninety, her first solo interview since tying the knot with William. "She always leaves a little gift or something in their room when we go and stay, and that just shows her love for her family."