Princess Beatrice and Princess Eugenie were both absent from the Together At Christmas Carol Service amid the fallout from their father, Andrew Mountbatten-Windsor's, downfall.
The pair did not attend the event pushed forward by Princess Kate, with Pippa Middleton also missing the ceremony.
Beatrice, 37, and Eugenie, 35, have retained their royal titles despite their disgraced father, Andrew, being dramatically stripped of his last remaining honours last October.
The move followed the publication of his accuser, Virginia Giuffre's, posthumous memoirs, and the US Government's release of documents from Jeffrey Epstein's estate.
Princess Beatrice and Eugenie were absent from Princess Kate's Christmas Carol Service | PATRENDING
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The former Duke of York has consistently denied any allegations surrounding him, and the Metropolitan Police previously considered that the sexual assault claims against Andrew were not sufficient to warrant further investigation.
Despite denying the allegations, 16 members of the US Congress sent a letter to Andrew, requesting that he testify about his knowledge surrounding Epstein.
It read: "The committee is seeking to uncover the identities of Mr Epstein's co-conspirators and enablers, and to understand the full extent of his criminal operations.
"Well-documented allegations against you, along with your long-standing friendship with Mr Epstein, indicate that you may possess knowledge of his activities relevant to our investigation.
Andrew has consistently denied any allegations surrounding him.
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"In the interest of justice for the victims of Jeffrey Epstein, we request that you cooperate with the committee's investigation by sitting for a transcribed interview with the committee."
Andrew missed the deadline set by the US Congress, with several members calling for him to come forward, including Suhas Subramanyam, who accused the former prince of "hiding from us".
Mr Subramanyam said: "If he is hoping that the story will just go away by ignoring us and being silent, he will be sorely disappointed".
Meanwhile, Democrat Congressman Raja Krishnamoorthi told Andrew to "come clean" when the request was issued on November 6.
Princess Beatrice and Princess Eugenie did not attend the carol service.
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"Come clean. Come before the US Congress, voluntarily testify," he told BBC Newsnight.
After being stripped of his royal titles, Andrew is due to leave Royal Lodge and move onto the Sandringham Estate.
King Charles is said to have been very keen to "protect" his nieces amid their father's downfall.
The pair have appeared to be trying to carry on with life as normal.
The King is said to have been very keen to 'protect' his nieces.
| GETTYPrincess Eugenie was seen recently taking the family to Winter Wonderland in Hyde Park, London.
The youngest daughter of the former Duke and Duchess of York was seen smiling with her children, August, four and Ernest, two.
The 35-year-old royal wore a fawn belted coat, with a grey top and baggy jeans.
She was in a jovial mood, enjoying a huge lollipop as she held onto her youngest son.
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