For the first time ever, Queen Camilla's family were expected to be at Sandringham but none of them were spotted on the annual walk to church on Christmas morning with the rest of the Royal Family
This article clears up the mystery of why Queen Camilla's family wasn't seen walking to church with the rest of the Royal Family on Christmas Day.
Although they were present at Sandringham for the first time ever, they chose not to participate in the public walk to church as they prefer to maintain their privacy. They still attended the church service with the rest of the royals.
Essentially, the missing family members were simply honoring their own preferences for a more private Christmas celebration.