Royal author Tom Quinn's next book covers Prince William and Kate Middleton's romance & growing up in the Royal Family.

The book reveals the pair's nicknames for each other: "babe" for William and "Duchess of Doolittle" for Kate.

William allegedly has shorter nicknames for Kate, including "Babykins" and "DoD."

Based on Queen Elizabeth II's critique, "Duchess of Doolittle" may be a jab at Kate's lack of a full-time career.

Kate allegedly fires back at William by calling him "baldy!"

William and Kate were together on and off from 2003 to 2010 before getting married in 2011.

Prince George, Princess Charlotte, and Prince Louis are their three children.

The book covers the history of the Royal Family, from the Tudors to the Cambridges.

Quinn spoke to palace staff, former aides, and royal insiders to get inside information