Princess Kate and Prince Harry were once close, but in recent days (via TV interviews and leaks) excerpts from Spare have been released, and it appears that the princess is not happy with her brother-in-law. Their relationship, sadly, could even be changed forever.

"Kate feels Harry's behavior is outrageous," a source told Us Weekly. 'She is appalled by him dragging her name through the mud and finds it hard to forgive him.'

One of the main accusations Harry seems to be hurling at Kate in "Spare" is that she and William actively encouraged him to dress as a Nazi instead of a British pilot at a 2005 costume party. When the pictures were released, the world was shocked by this very insensitive costume choice, and Harry recently called it one of his "biggest mistakes."

Of his decision to wear the costume published in Spare, the prince wrote: "I was very much disappointed in the way they dressed me. It was a Nazi uniform, they said. I rented it, put on an even more ridiculous mustache, and went home. I put it all on. We both howled.

In his book, Harry also mentions a fight between Kate and his wife Meghan Markle.

As Kate celebrates her birthday today, royal expert Duncan Larcombe once told OK!

"There was once a time when Harry was instrumental in the couple's celebrations and fun, but those days are long past."

Spares will be officially released tomorrow, January 10.