"Prince William and his brother Harry have a slow-burning inner rage about press intrusion, as was revealed in Harry's interview after his return from serving in Afghanistan," he told HELLO!.
"How can it be otherwise, when Kate is enduring the same treatment that was meted out to Diana over 30 years ago?"
31 years ago, Ken also snapped a 20-year-old Princess Diana and Prince Charles in images almost identical to those that emerged of Prince William and his wife in Mustique.
For the full gallery of photos, download HELLO!'s iPad edition, out now
Picturing Diana, who was pregnant at the time, in her bikini naturally caused controversy, and Ken tells HELLO! there are parallels between the late Princess of Wales and the woman who would have been her daughter-in-law.
Ken admits that he took similar intrusive photographs of Princess Diana and Prince Charles in Eleuthra, a private island in the Caribbean, when the 20-year-old Princess was pregnant with William.
"I only have one regret in my career… that event 31 years ago where I got carried away and intruded into a young girl's life," he told the magazine.
"I went on to do other things but the intrusion continued until Diana's death in Paris."
"The photographer who took the current photographs of Kate and William won't be aware of any of this history. I hope in 30 years' time he won't have the same regrets."
Ken Lennox has been photographing members of the royal family for the past 53 years and recently captured Kate Middleton at the Natural History Museum on the eve of her pregnancy announcement.
To read more of the interview with Ken Lennox and other royal commentators pick up a copy of HELLO!, issue 1265, out now.