Kate Middleton Pregnant: How George Changed Princes William and Harry

September 8, 2014 2:10 PM EDT

With the news that the Duchess of Cambridge, Kate Middleton, is pregnant with a second royal baby, a new biography of Prince Harry sheds light on the evolution of his relationship with his older brother, Prince William, Duke of Cambridge, since the birth of Prince George last July.

“It’s fantastic to have an addition to the family,” Harry said about his nephew, as royal-family biographer Penny Junor writes in Prince Harry: Brother, Soldier, Son. “I only hope my brother knows how expensive my baby-sitting charges are.”

And if Will’s change in behavior since George’s birth is any indication, the birth of his second child will likely mean Will and Harry will spend less time playing around with friends at clubs and more time playing with babies. Junor writes in Prince Harry:

William’s focus has changed. He is no longer in the military, no longer up for partying till dawn, or tripping over guy-ropes in the early hours at Glastonbury. He is more interested in getting an unbroken night of sleep and listening to George’s growing vocabulary.

The biography quotes “a friend” adding that Prince Harry “loves” having dinner with Will, Kate and George and says that’s basically what the brothers’ nights out are like now, even though Harry does not appear to show signs of settling down himself anytime soon.

It would be a different night from the one they would have spent three or four years ago, which would have been, ‘Who can remain standing longest?’ … They are very, very close and Harry loves the whole domestic bit which his brother’s doing now … I think he sees what his brother’s getting out of it …

The book will be released tomorrow, ahead of Prince Harry’s 30th birthday next week.

See Kate Middleton's Best Pregnancy Looks

Catherine, Duchess of Cambridge welcomes the President of Singapore Tony Tan Keng Yam at the Royal Garden Hotel on Oct. 21, 2014 in London.Chris Jackson—Getty Images

The Duchess Of Cambridge Visits Hope House — Catherine, Duchess of Cambridge visits Hope House, an Action on Addiction women's treatment centre on February 19, 2013 in London.Neil Mockford—FilmMagic/Getty Images

Prince William and Duchess Kate in Scotland — Catherine, Duchess of Cambridge visits the Donald Dewar Leisure Centre in Drumchapel to launch a new Scottish project for their Foundation in Glasgow on April 4, 2013.Rpe-Albert Nieboer—Picture-Alliance/dpa/AP

Catherine, Duchess of Cambridge during the National Review of Queen's Scouts at Windsor Castle in Berkshire on April 21, 2013. Olivia Harris—AFP/Getty Images

Catherine, Duchess of Cambridge arriving for a visit the National Portrait Gallery in London to celebrate the work of The Art Room charity on April 24, 2013. John Stillwell—AP

Catherine, Duchess of Cambridge arrives for her visit to Warner Bros studios in Leavesden, Herts where the popular Harry Potter movies were produced on April 26, 2013.Chris Jackson—AP

Catherine, Duchess of Cambridge during her visit to Naomi House Children's Hospice in Winchester, Hampshire, England during Children's Hospice Week on April 29, 2013.Steve Parsons—AP

Catherine, Duchess of Cambridge attends a Garden Party in the grounds of Buckingham Palace, hosted by Queen Elizabeth II on June 30, 2013 in London.John Stillwell—AP

Queen Elizabeth II's Birthday Parade: Trooping The Colour — Catherine, Duchess of Cambridge stands on the balcony of Buckingham Palace during the annual Trooping the Colour Ceremony on June 15, 2013 in London, England. Max Mumby—Indigo/Getty Images

Duchess to miss friends wedding — Catherine, Duchess of Cambridge attends the Princess Cruises ship naming ceremony at Ocean Terminal on June 13, 2013 in Southampton, England.Chris Ison—AP

How a Baby Changed William and Harry’s Royal Relationship

See Kate Middleton's Best Pregnancy Looks

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