Meghan Markle was reportedly 'not satisfied' with the Royal Family response to racism concerns.
It comes after the Duchess of Sussex is understood to have sent official correspondence in the wake of the couple's explosive interview with Oprah Winfrey.
The interview saw Prince Harry and his wife sit down for their first major interview since quitting as working royals with one of the biggest talking points when they revealed a senior royal questioned the colour of their unborn son’s skin.
The couple sent shockwaves through the British monarchy when they spoke of their disgust at "concerns and conversations about how dark his skin might be when he's born".
The King is believed to be the only senior member of the family that made contact with Meghan following the interview - with Meghan thanking him for his response.
However, a source claimed the Duchess felt she hadn't "received a satisfactory response to her concerns, and that is believed to be one factor in her decision not to attend the Coronation".
The source went on to suggest the letters "make clear the identity of the senior member of the family who made the comment".
It has been reported that the King and Meghan accepted the remark was not made with malice.
They added that Meghan's feelings about the supposed inadequate response was a factor in her decision not to attend the Coronation on May 6, The Telegraph reports.
Meghan will be staying with their children Prince Archie and Princess Lilibet, with her son celebrating his fourth birthday on the same day as the Coronation.
An insider told The Mirror the King is "delighted" at Harry's choice to travel to the UK for the occasion, adding that the Duke of Sussex "would have deeply regretted" not attending it.
But a royal commentator has said Meghan's decision to miss the Coronation makes her feelings about the Royal Family "obvious," expert Daniela Elser wrote in news.com.au.
"Their decision for Meghan not to go could have serious repercussions, not least when it comes to their Sussex titles.
"In making the choice to not go and to not show her support for her father-in-law, to not be there for the one of the biggest moments for the monarchy in the better part of a century, she is making her position in regards to the institution pretty damn obvious.
"Meghan seems to be taking an abundantly crystal clear stance on what sort of relationship she wants to have with her husband's family, i.e., pretty much none."
