The Duchess of Cambridge’s relationship with William, 38, has been compared to the Duke of Edinburgh, 99, and the Queen, 94. Royal biographer Penny Junor said Kate, 38, has “a lot to say” but “doesn’t outshine” her husband.
Ms Junor told People magazine: “She’s never trying to outshine him in any way.
“I think that Kate is a bit like Prince Philip supporting the Queen. She doesn’t outshine William but still has a lot to say herself.”
Royal author Sarah Gristwood added that Kate is a “supportive figure” to William, who is second in line to the throne.
She said: “In one sense hers and William’s was a modern royal marriage, in that it was a love match.
William admitted being overwhelmed at times but said he and Kate support each other.
He said: “Having children is the biggest life-changing moment, it really is.
“And I agree with you, I think when you’ve been through something traumatic in life – and that is like you say your dad not being around, my mother dying when I was younger – your emotions come back in leaps and bounds because it’s a very different phase of life.
“And there’s no one there to help you, and I definitely found it very, at times, overwhelming.
“Me and Catherine particularly, we support each other and we go through those moments together and we kind of evolve and learn together.
“But I do agree with you, I think emotionally things come out of the blue that you don’t ever expect or maybe you think you’ve dealt with and so I can completely relate to what you’re saying about children coming along, it’s one of the most amazing moments of life but it’s also one of the scariest.”
William was speaking to former professional footballer Marvin Sordell who said he struggled when he became a parent for the first time a few years ago having grown up without a father.
The Cambridges are parents to Prince George, six, Princess Charlotte, five, and two-year-old Prince Louis.