Meghan Markle's estranged father, Thomas Markle, is "unable to speak" after suffering a stroke.
The 77-year-old reportedly fell ill in his home in Mexico and was taken to hospital via an ambulance overnight.
"We are praying," Thomas' daughter Samantha Markle, who along with brother Thomas Jr rushed to his bedside, told The Sun.
"My father is recovering in hospital. We ask for privacy for the family, for his health and wellbeing. He just needs peace and rest. Godspeed. We are praying."
The former Hollywood lighting director was photographed getting wheeled into an ambulance via a trolley and was ferried to the Mexican border for treatment in San Diego and California.
Photographer Karl Larsen, a friend of Thomas', revealed on the pair's Remarkable Friendship podcast: "Thomas Sr thought he had a stroke and was taken to hospital. He wrote it on a piece of paper because he can't speak right now."
"He lost his voice, I don't know why, so he had to write it down and he gave it to someone who he was with. He was just barely present enough to write on a piece of paper."
The tragic news comes a week before Thomas was due to fly out to the UK to celebrate the Queen's Platinum Jubilee.
Prince Harry, 37, and Meghan, 40, are also expected to attend, but were to fly separately.
"We were due to leave for London to be there for the Jubilee on Monday. Now it's all up in the air, I don't know what will happen. I can't possibly see how that would still be on," Karl said.
"I was with Thomas when something very similar happened four years ago before Harry and Meghan's wedding."
The Duchess of Sussex is yet to comment on her father's stroke, and they haven't spoken for four years.
Thomas still hasn't met his two grandchildren, Archie, three and Lilibet, 11 months.