Prince William's rumored affair with model Rose Hanbury has strained his marriage with Kate.

The Duke and Duchess have continued to show themselves as a normal couple to avoid doubts.

Royal author Tom Quinn's book, "Golden Youth," reveals why Prince William has stayed with Kate.

William's relationship with Diana was not stable due to her desperation for love.

Because he grew up with nannies and governesses, William did not become as attached to Diana as many believe.

Kate represents a solidity that the late Queen represented - constant and never complaining.

William, who is emotional and prone to losing his head, finds Kate's stability appealing.

Kate helps William lead a peaceful life, something that no other woman could achieve.

Kate offers something unique to William, which is why he has stayed with her.