Insiders told the Daily Express the children of the late Princess Margaret will be relegated to the servant's quarters. The queen's nephew, David Armstrong-Jones, or Viscount Linley, and niece, Lady Sarah Chatto, who now have spouses and children of their own, have been quartered there before.
Some of the Sandringham servants will have to double up or move temporarily to cottages on the large estate.
Prince William and his wife spent Christmas with her family last year. This year, they will be at Sandringham with their new baby, Prince George.
"Sandringham is a large house but everyone will be crammed in like sardines," an insider told the Express. "There are just so many young royals now with children, and the numbers keep going up."
The schedule includes a formal Christmas Eve dinner followed by the opening of presents, a German tradition adopted by Queen Victoria and her husband, Prince Albert. On Christmas Day, the royals attend church and enjoy a hearty lunch, with a more informal evening meal since the staff gets the rest of the day off.
On Boxing Day, Dec. 26, Prince Philip leads his descendents in the traditional shooting party.
The queen and Philip traveled to Norfolk by train Thursday. The rest of the family usually arrives in reverse order of precedence, with Prince Charles and his wife appearing Christmas Eve, the Express said.