The news was confirmed by Thomas' close friend Karl Larsen, who shares a YouTube channel with the 77-year-old. He confirmed that Thomas had been admitted to the hospital on Tuesday morning following the stroke.
Meghan's father was due to fly out to the United Kingdom ahead of the Queen's Platinum Jubilee, where he would have met his grandchildren, Archie and Lilibet, for the first time.
WATCH: Prince Harry talks about his and Meghan Markle's visit with the Queen
Karl added that Thomas had been "looking forward" to the family time.
Last year, the Duchess of Sussex opened up about her feelings of "betrayal" during an appearance on Oprah With Meghan and Harry: A CBS Primetime Special.
"When I asked him, he said, 'No, absolutely not [that he hadn't been talking to the tabloids],'" Meghan revealed. But when she probed her father further, saying that she and Harry had offered to try and "kill" the news story if he was in fact telling the truth, Thomas wasn't able to say that he was.
Thomas and Meghan have an estranged relationship
"I said, I just need you to tell me and if you tell me the truth we can help. And he wasn't able to do that," said Meghan.
Although Harry and Meghan, alongside their two children will be back for the Queen's Platinum Jubilee, they won't be taking part in the Trooping the Colour ceremony as they aren't working royals.
A spokesman for Buckingham Palace said: "After careful consideration, The Queen has decided this year's traditional Trooping the Colour balcony appearance on Thursday 2 June will be limited to Her Majesty and those members of the Royal Family who are currently undertaking official public duties on behalf of the Queen."
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