Prince William is fearful for his brother after Harry and Meghan spoke about the hardships of life in the public eye, it has been reported.
The Duke and Duchess of Sussex admitted they were struggling with the headlines and attention from British tabloid newspapers in a documentary which aired on ITV on Sunday night.
Meghan also revealed her friends told her not to marry Harry, warning her she "shouldn't do it because the British tabloids will destroy your life".
She told of how she was "not okay", while Prince Harry said his mental health was under "constant management".
A Palace source told the BBC Prince William is worried about his younger brother and his sister-in-law, and hopes they are both "all right".
The source said there is a view that Harry and Meghan are "in a fragile place".
There was no comment from Kensington Palace on the documentary, which followed the royal couple on their African tour.
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Earlier this year, Harry and Meghan split from their joint charity with William and Kate.
In the documentary, Prince Harry, answered a question about rumours of a rift between himself and the Duke of Cambridge, saying he and his brother are "on different paths" and have "good days" and "bad days".
The Duke of Sussex said "inevitably stuff happens" – particularly with such a high-profile role and a family that lives under pressure.
He told the ITV documentary Harry & Meghan: An African Journey: "We are brothers. We will always be brothers.
"We are certainly on different paths at the moment but I will always be there for him as I know he will always be there for me.
"We don't see each other as much as we used to because we are so busy but I love him dearly.
"The majority of the stuff is created out of nothing but as brothers, you know, you have good days, you have bad days."
After the split was announced earlier this year, sources denied any feud – saying the move was "largely about preparing both couples for their future roles, which are obviously on divergent tracks".