While Princess Diana's close bond with her sons Prince William and Harry was always apparent, there's one thing that many people may not know about Harry's birth.

Prince Charles "desperately" wanted a little girl, so Diana, knowing that she was having a boy, kept Harry's gender a secret throughout her pregnancy.

Diana gave birth to a baby boy, Henry Charles Albert David Mountbatten-Windsor, after nine hours of labor and zero drugs in September 1984. In Andrew Norton's book "Diana: Her True Story," Charles' heartbreaking reaction to Harry's arrival was revealed.

"Charles always wanted a girl," Diana said. "Harry was a boy. His first comment was, 'Oh God, it's a boy.' His second: 'And he's even got red hair.'"

22 PHOTOS Princess Diana with her sons See Gallery Princess Diana with her sons VENICE, ITALY - MAY 5: (FILE PHOTO) (L-R) Diana the Princess of Wales holds her son Harry, whilst looking at Prince William held by his father Prince Charles on May 5, 1985 in Venice, Italy. Prince William will celebrate his 21st birthday on June 21, 2003. (Photo by Georges de Keerle/Getty Images) Princes William and Harry with their mother, Diana, Princess of Wales (1961 - 1997) in the garden of Highgrove House in Gloucestershire, 18th July 1986. William is wearing a Dallas Cowboys t-shirt.(Photo by Tim Graham/Getty Images) TETBURY, UNITED KINGDOM - JULY 18: Princess Diana At Highgrove With Prince William And Prince Harry Dressed In Miniature Parachute Regiment Uniforms And Playing On Their Slide In The Garden (Photo by Tim Graham/Getty Images) TETBURY, UNITED KINGDOM - JULY 18: Princess Diana With Her Sons Prince William And Prince Harry Playing With A Playhouse In The Garden Of Their Home Highgrove (Photo by Tim Graham/Getty Images) The Prince and Princess of Wales on holiday with their children, Princes William and Harry, at the Spanish royal residence Marivent Palace, August 1987. (Photo by Terry Fincher/Getty Images) The Princess of Wales arriving at Aberdeen airport with her sons William and Harry for a holiday at Balmoral Castle, August 1986. Princess Diana is wearing a polo motive sweater by Mondi. (Photo by Jayne Fincher/Getty Images) UNITED KINGDOM - DECEMBER 01: Prince Charles, Prince of Wales and Diana, Princess of Wales at home in Kensington Palace with their sons Prince William and Prince Harry (Photo by Tim Graham/Getty Images) LONDON, UNITED KINGDOM - SEPTEMBER 16: Princess Diana And Prince William Leaving After Delivering Prince Harry To Mrs. Mynor's Nursery School. (Photo by Tim Graham/Getty Images) LONDON, UNITED KINGDOM - JUNE 11: Diana, Princess Of Wales, Holding A Young Prince Harry In Her Arms As She Watches Trooping The Colour With Prince William And Princess Margaret From The Balcony Of Buckingham Palace. (Photo by Tim Graham/Getty Images) BALMORAL, SCOTLAND - AUGUST 18: Diana, Princess of Wales, and Prince Harry play on the banks of the River Dee, near Balmoral Castle.during a Summer vacation, on August 18, 1987, in Balmoral, Scotland. (Photo by Julian Parker/UK Press via Getty Images) NECKER ISLAND, BRITISH VIRGIN ISLANDS - JANUARY 9: Diana, Princess of Wales, with Prince Harry ( centre ), and her Niece's and Nephew's on holiday on Necker Island , on January 9, 1989 in Necker Island, British Virgin Islands. (Photo by Julian Parker/UK Press via Getty Images) BATH - MAY 30: (FILE PHOTO) Prince William, Diana, Princess of Wales, Prince Harry and Charles, Prince of Wales, attend the wedding of the Duke of Hussey's daughter in May, 1989 in Bath, England. (Photo by Anwar Hussein/Getty Images) LONDON - SEPTEMBER 12: (FILE PHOTO) Princess Diana with her sons Prince William and Prince Harry at Wetherby School on September 12, 1989 in London, England. It is Prince Harry's first day at school. (Photo by Anwar Hussein/Getty Images) Diana, The Princess Of Wales Takes Her Sons, Prince'S William, And Harry Out On The Boat ' Maid Of The Mist ' To View Niagara Falls. (Photo by Julian Parker/UK Press via Getty Images) CHERTSEY, UNITED KINGDOM - APRIL 18: Diana, Princess of Wales, with Prince Harry, on the Depth Charge ride at Thorpe Park, Theme Park, on April 18, 1992 in Chertsey United Kingdom . (Photo by Julian Parker/UK Press via Getty Images) LECH, AUSTRIA - APRIL 10: Princess Diana With Princes William & Harry Skiing In Lech, Austria (Photo by Tim Graham/Getty Images) Diana Princess Of Wales, Prince William & Prince Harry Visit The 'Thorpe Park' Amusement Park. (Photo by Julian Parker/UK Press via Getty Images) AUSTRIA - MARCH 30: Lech: Princess Diana, sons William and Harry going to restaurant in calash In Lech, Austria On March 30, 1993. (Photo by Laurent SOLA/Gamma-Rapho via Getty Images) LECH, AUSTRIA - MARCH 27: Princess Diana With Prince William & Prince Harry In Sleigh During Ski Holiday In Lech, Austria. Behind Are Diana's Friends Kate Menzies And Catherine Soames (Photo by Tim Graham/Getty Images) LONDON, UNITED KINGDOM - AUGUST 19: Princess Diana, Prince Harry [ Waving ] And Prince William Watching The Parade Of Veterans On V J Day, The Mall, London. Designer Of Diana's Suit - Tomasz Starzewski (please Check - People Magazine, 04/12/1999) (Photo by Tim Graham/Getty Images) EMBARGOED TO 0001 Sunday July 23, 2017. NO USE AFTER MONDAY JULY 31, 2017. NEWS EDITORIAL USE ONLY. NO USE ON THE FRONT COVERS OF ANY UK OR INTERNATIONAL MAGAZINES. NO COMMERCIAL USE (including any use in merchandising, advertising or any other non-editorial use including, for example, calendars, books and supplements). This photograph (whose copyright is vested in the Duke of Cambridge and Prince Harry) is provided to you on condition that you will make no charge for the supply, release or publication of it and that these conditions and restrictions will apply (and that you will pass these on) to any organisation to whom you supply it. All other requests for use should be directed to the Press Office at Kensington Palace in writing. This photograph released by Kensington Palace, from the personal photo album of the late Diana, Princess of Wales, shows the princess holding Prince William whilst pregnant with Prince Harry, and features in the new ITV documentary 'Diana, Our Mother: Her Life and Legacy', which airs on ITV at 21.00hrs on Monday 24th July. EMBARGOED TO 0001 Sunday July 23, 2017. NO USE AFTER MONDAY JULY 31, 2017. NEWS EDITORIAL USE ONLY. NO USE ON THE FRONT COVERS OF ANY UK OR INTERNATIONAL MAGAZINES. NO COMMERCIAL USE (including any use in merchandising, advertising or any other non-editorial use including, for example, calendars, books and supplements). This photograph (whose copyright is vested in the Duke of Cambridge and Prince Harry) is provided to you on condition that you will make no charge for the supply, release or publication of it and that these conditions and restrictions will apply (and that you will pass these on) to any organisation to whom you supply it. All other requests for use should be directed to the Press Office at Kensington Palace in writing. This photograph released by Kensington Palace, from the personal photo album of the late Diana, Princess of Wales, shows the princess and Prince Harry on holiday and features in the new ITV documentary 'Diana, Our Mother: Her Life and Legacy', which airs on ITV at 21.00hrs on Monday 24th July. Up Next See Gallery Discover More Like This HIDE CAPTION SHOW CAPTION of SEE ALL BACK TO SLIDE

While Charles saw his comments as a joke, Diana was extremely hurt and offended by it -- not only did she just endure nine hours of labor but her older sisters and younger brother all had red hair (it's a trait that runs in the Spencer family).

At Harry's christening in December, Charles reportedly told Diana's mother, "We were so disappointed -- we thought it would be a girl."

Diana also made another heartbreaking confession about the weeks leading up to Harry's birth -- Charles and her were "the closest we've ever, ever been and ever will be."

But after Harry's birth, everything changed: "Then, suddenly, as Harry was born, it just went bang, our marriage. The whole thing went down the drain."

RELATED: Princess Diana and her fabulous travels:



43 PHOTOS Princess Diana and her fabulous travels See Gallery Princess Diana and her fabulous travels GIBRALTAR- AUGUST 01: Prince Charles, Prince of Wales and Princess Diana, Princess of Wales, wearing a Donald Campbell dress, leave for their honeymoon cruise on the Royal Yacht Britannia on August 01, 1981 in Gibraltar. (Photo by Anwar Hussein/Getty Images) The Prince and Princess of Wales leave Gibraltar on the Royal Yacht Britannia for their honeymoon cruise, 1st August 1981. The Princess wears a Donald Campbell dress. (Photo by Tim Graham/Getty Images) BALMORAL, UNITED KINGDOM - AUGUST 19: The Prince And Princess Of Wales On Their Honeymoon In Balmoral, Scotland (Photo by Tim Graham/Getty Images) BALMORAL, UNITED KINGDOM - AUGUST 19: Prince Charles With His Arm Around Princess Diana As They Sit On A Style During Their Honeymoon At Balmoral In Scotland.the Princess Is Wearing A Suit Designed By Bill Pashley With A Pair Of Shoes By The Chelsea Cobbler. (Photo by Tim Graham/Getty Images) 15th June 1983: Charles, Prince of Wales, and Diana, Princess of Wales, (1961 - 1997) on holiday in Nova Scotia. (Photo by Central Press/Getty Images) FRANCE - UNDATED: Princess Diana, Princess of Wales poses in a bikini whilst on holiday in the South of France. (Photo by Anwar Hussein/WireImage) VIRGIN ISLANDS - UNDATED: Princess Diana, Princess of Wales enjoys a swim in the Virgin Islands. (Photo by Anwar Hussein/WireImage) FRANCE: The Princess of Wales enjoys a swim in the South of France. (Photo by Anwar Hussein/WireImage) *** Local Caption *** KLOSTERS, SWITZERLAND - FEBRUARY 1986: Princess Diana, Princess of Wales, wearing red ski gear and a red and white head band, enjoys a skiing holiday in Klosters, Switzerland in February 1986. (Photo by Anwar Hussein/WireImage) (From left to Right) Prince Charles, Princess Diana, The Duchess of York Sarah Ferguson and The Duke of York Prince Andrew posing for photographers on their skiing holiday at the Swiss resort of Klosters. Wednesday 17th February 1987. (Photo by Kent Gavin/Mirrorpix/Getty Images) KLOSTERS, SWITZERLAND - FEBRUARY 17: The Duchess Of York (sarah Ferguson) And Princess Diana Having Fun On Holiday In Klosters. (Photo by Tim Graham/Getty Images) Members of the British Royal Family on a ski holiday, (L-R) Prince Charles, Prince Andrew, Princess Diana and the Duchess of York, in Grisons, Switzerland, February 17th 1987. (Photo by Tim Graham/Getty Images) Princess Diana on a ski holiday in Klosters, Switzerland, February 6th 1986. (Photo by Tim Graham/Getty Images) KLOSTERS, SWITZERLAND - FEBRUARY 06: Diana, Princess of Wales, wearing red ski gear and a red and white head band, enjoys a skiing holiday on February 06, 1986 in Klosters, Switzerland. (Photo by Anwar Hussein/Getty Images) MAJORCA-AUGUST 10: (FILE PHOTO) Princess Diana, Princess of Wales with Prince William and Prince Harry on holiday in Majorca, Spain on August 10, 1987. Also present were the Spanish Royal Family and the Prince of Wales. (Photo by Anwar Hussein/Getty Images) MAJORCA, SPAIN - AUGUST 08: Prince Charles And Princess Diana With Prince William And Prince Harry On Holiday In Majorca. Also Present Are Queen Sofia Of Spain And Infanta Elena. (Photo by Tim Graham/Getty Images) PALMA, SPAIN - AUGUST 10: Diana, Princess of Wales poses with Queen Sofia of Spain during a summer holiday in Majorca on August 10, 1987 in Palma, Spain. (Photo by Anwar Hussein/Getty Images) Princess Diana (1961 - 1997, left) with the Duchess of York during a skiing holiday in Klosters, Switzerland, 9th March 1988. (Photo by James Andanson/Sygma via Getty Images) Left to right: the Duchess of York, Princess Diana (1961 - 1997) and Prince Charles during a skiing holiday in Klosters, Switzerland, 9th March 1988. (Photo by James Andanson/Sygma via Getty Images) NECKER ISLAND, BRITISH VIRGIN ISLANDS - JANUARY 9: Diana, Princess of Wales, with Prince Harry on holiday on Necker Island , on January 9, 1989 in Necker Island, British Virgin Islands. (Photo by Julian Parker/UK Press via Getty Images) NECKER ISLAND, BRITISH VIRGIN ISLANDS - JANUARY 9: Diana, Princess of Wales, on holiday on Necker Island , on January 9, 1989 in Necker Island, British Virgin Islands. (Photo by Julian Parker/UK Press via Getty Images) NECKER ISLAND, BRITISH VIRGIN ISLANDS - JANUARY 9: Diana, Princess of Wales, on Necker Island , on January 9, 1989 in Necker Island, British Virgin Islands. (Photo by Julian Parker/UK Press via Getty Images) NECKER ISLAND, BRITISH VIRGIN ISLANDS - JANUARY 9: Diana, Princess of Wales, on Holiday on Necker Island , on January 9, 1989 in Necker Island, British Virgin Islands. (Photo by Julian Parker/UK Press via Getty Images) NECKER ISLAND - APRIL 11: Princess Diana In Leopardskin Swimming Costume And Sarong On Holiday In Necker Island In The Caribbean (Photo by Tim Graham/Getty Images) The Prince and Princess of Wales holiday on a yacht with King Constantine II of Greece, 1990. (Photo by Georges De Keerle/Getty Images) NECKER ISLAND, BRITISH VIRGIN ISLANDS - APRIL 11: Diana, Princess of Wales, with Prince William, on Holiday In Necker Island In The Caribbean, on April 11, 1990, in the British Virgin Islands. (Photo by Julian Parker/UK Press via Getty Images) SPAIN - AUGUST 15: Princess Diana on holiday in Majorca with King Constantine of Greece and his daughter, Princess Theodora on the King's yacht, Fortuna. (Photo by Tim Graham/Getty Images) MAJORCA, SPAIN - AUGUST 15: Princess Diana On Board The Yacht Fortuna On Summer Holiday In Majorca (Photo by Tim Graham/Getty Images) MAJORCA, SPAIN - AUGUST 15: Diana, Princess of Wales, on board the yacht of King Juan Carlos of Spain 'Fortuna' on summer holiday on August 15, 1990 in Majorca, Spain (Photo by Georges De Keerle/Getty Images) SAINT KITTS AND NEVIS - JANUARY 1993: Diana, The Princess of Wales walks in the sea on January 1993 in the Island of Nevis. (Photo by Julian Parker/UK Press via Getty Images) Princess Diana (1961 - 1997) in the surf off the Island of Nevis, during a Caribbean holiday, 2nd January 1993.(Photo by Thierry Orban/Sygma via Getty Images) SAINT KITTS AND NEVIS - JANUARY 1993: Diana, The Princess of Wales walks in the sea on January 1993 in the Island of Nevis. (Photo by Julian Parker/UK Press via Getty Images) The Princess of Wales (C) watches for a wave while surfing at Indian Castle Beach 02 January 1993. Princess Diana is vacationing with her sons William and Harry. (Photo credit should read PAUL J. RICHARDS/AFP/Getty Images) SAINT KITTS AND NEVIS - JANUARY 1993: Diana, The Princess of Wales walks in the sea on January 1993 in the Island of Nevis. (Photo by Julian Parker/UK Press via Getty Images) GIZA, EGYPT - MAY 12: Diana Princess of Wales visiting the Pyramids in Giza during an official tour of Egypt. (Photo by Tim Graham/Getty Images) GIZA, EGYPT - MAY 12: Diana Princess of Wales visits the Pyramids in Giza during an official tour of Egypt. (Photo by Tim Graham/Getty Images) SAINT KITTS AND NEVIS - JANUARY 1993: Diana, The Princess of Wales walks in the sea on January 1993 in the Island of Nevis. (Photo by Julian Parker/UK Press via Getty Images) LECH, AUSTRIA - MARCH 25: Diana, Princess Of Wales, On A Spring Ski-ing Holiday With Her Sons, Prince William And Prince Harry, And Her Friend Kate Menzies. (Photo by Tim Graham/Getty Images) AUSTRIA - MARCH 26: Diana, Princess of Wales running whilst on a skiing holiday in Lech, Austria (Photo by Tim Graham/Getty Images) Princess Diana (back row, R), along with her friends Kate Menzies (back row C) and Catherine Soames (back row, L), rides 26 August 1993 the Splash Mountain ride at Disney World's Magic Kingdom during the third day of their vacation. Front row left is Prince Harry, son of Princess Diana. Other passengers are unidentified. (Photo credit should read BOB PEARSON/AFP/Getty Images) Photo taken on July 14, 1997 shows Britain's Lady Diana taken by an unidentified young girl for a jet-ski ride off the property of her friend Dodi Al-Fayed in Saint Tropez, on the French Riviera. Diana, Princess of Wales, and her companion, the Egyptian millionaire film-producer Dodi al-Fayed, died in Paris early 31 August after a midnight car crash. / AFP PHOTO / Patrick HERTZOG (Photo credit should read PATRICK HERTZOG/AFP/Getty Images) Photo taken on July 14, 1997 shows Britain's Lady Diana taken by an unidentified young girl for a jet-ski ride off the property of her friend Dodi Al-Fayed in Saint Tropez, on the French Riviera. Diana, Princess of Wales, and her companion, the Egyptian millionaire film-producer Dodi al-Fayed, died in Paris early 31 August after a midnight car crash. / AFP PHOTO / Patrick HERTZOG (Photo credit should read PATRICK HERTZOG/AFP/Getty Images) ST TROPEZ, FRANCE - JULY 17 1997: (FILE PHOTO) Diana, Princess of Wales and son HRH Prince William are seen holidaying with Dodi Al Fayed (not pictured) in St Tropez in the summer of 1997, shortly before Diana and Dodi were killed in a car crash in Paris on August 31, 1997. The inquests into both of their deaths are due to start in early 2004. (Photo by Michel Dufour/WireImage) Up Next See Gallery Discover More Like This HIDE CAPTION SHOW CAPTION of SEE ALL BACK TO SLIDE

Diana went on to admit that "something inside me closed off. By then, I knew Charles had gone back to his lady."

If you recall, that "lady" was later revealed as Camilla Parker Bowles.

Charles began an affair around 1978 or 1979 with his now-wife Camilla while still married to Diana. Charles and Diana separated in 1992 and officially got divorced in 1996. However, a recently published book, "Prince Charles: The Passions and Paradoxes of an Improbable Life," divulged that there was trouble in paradise as early as their honeymoon.

As his mother's 20th death anniversary nears, it has been rumored that Prince Harry has proposed to his girlfriend of over a year, Meghan Markle. More on that in the video above.

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