Prince William and Duchess Camilla were struggling with their new sibling's relationship back in those days.
A royal expert says Camilla and Prince Charles, who compromised their marriages to be with each other, hurt their children's feelings.
Author Katie Nicholl, in her 2010 book 'Harry and William', said the Duke touched on the 'terrible feud' between William and Laura Parker Bowles.
She said: "William and Laura used to have terrible fights about who to blame for their broken homes."
Ms Nicholl quoted a family friend of the royal family as saying: "William would blame Camilla for all the injuries he inflicted on his mother, which would send Laura into a rage.
"Laura had none of it. She would take a tough line and fire back at William saying 'Your father ruined my life.'"
Royal biographer Penny Junor added in her book: "I think the relationship between them all is hot now, but if I'm being honest, it wasn't. I think they found it hard.
"To be fair to Camilla, she never tried to be a mom but she was the 'other woman' and she was there and taking daddy's time."