Meghan Markle and her mother, Doria Ragland arrive at Cliveden House Hotel on the National Trust's Cliveden Estate to spend the night before her wedding to Prince Harry on May 18, 2018 in Berkshire, England.
In contrast, Kate Middleton's parents have also been guests at the Sandringham Christmas morning church service but typically stay with their daughter and Prince William at their nearby home nearby, instead.
"When you meet Doria, it all falls in place".
When the 92-year-old Monarch heard about it she told Doria she could come to Sandringham.
Doria said she was thrilled at Meghan's pregnancy, saying she was "very happy about this lovely news and is looking forward to welcoming her first grandchild".
Last year, Elizabeth made a historic exception by inviting Markle, and now she is breaking royal tradition again for Markle's mother.
Mr Markle pulled out because of health problems just days before she was due to walk down the aisle and admitted he had staged paparazzi pictures.
He also expressed a fear he could die soon and that it was the longest he and Meghan had gone without speaking.
A spokesperson for Buckingham Palace declined to comment today.