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- Prince William missed a Service of Thanksgiving on Tuesday due to "a personal matter."
- William's absence comes as King Charles III and Kate Middleton continue to miss public duty.
- Experts previously told Business Insider the royal family needs William while his father is sick.
Prince William didn't attend a royal engagement on Tuesday.
Queen Camilla and other members of the royal family attended a Service of Thanksgiving for King Constantine of Greece at St George's Chapel at Windsor Castle. Constantine died at 82 in January. He and Charles were second cousins, and Constantine was one of William's godfathers.