Britain’s Prince Harry was deeply concerned about what the future held for him before American actress Meghan Markle came along.

After a whirlwind romance, the couple tied the knot in a televised ceremony in May 2018. Markle, 37, and Harry, 34, are expecting their first child sometime this spring.

MEGHAN MARKLE HASN'T RECONCILED WITH HER FATHER

“Harry, at one point, was genuinely worried that he was going to be left on the shelf,” royal expert Katie Nicholl told Fox News.

Meghan Markle and Prince Harry have received hundreds of gifts. (Getty Images)

Nicholl, a British best-selling author and royal correspondent for Vanity Fair, recently published “Harry and Meghan: Life, Loss, and Love,” which presents an in-depth look at Harry’s romance with Markle, now the Duchess of Sussex, and how their high-profile union is reshaping the monarchy. It features interviews with friends close to the couple, those who have worked with Harry, as well as palace aides, among others.

Nicholl shared Harry could vividly see what was missing in his life.

“His brother [Prince William] was happily married with children,” she explained. “Many of his friends, who up until that point had been eternal bachelors, were getting engaged, getting married. I think Harry genuinely worried about that, and one of the reasons he worried about that was because he wanted to find his life partner, and he wanted to be a dad. Harry wanted children for a very long time.”

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SUVA, FIJI - OCTOBER 23: Prince Harry, Duke of Sussex and Meghan, Duchess of Sussex arrive for the State dinner on October 23, 2018 in Suva, Fiji. The Duke and Duchess of Sussex are on their official 16-day Autumn tour visiting cities in Australia, Fiji, Tonga and New Zealand. (Photo by Ian Vogler - Pool/Getty Images)

Meghan Markle and Prince Harry in Fiji in October 2018 (Getty)

Multiple reports first surfaced that Harry and Markle were dating in October 2016 after they were introduced by a mutual friend. In November 2017, Harry’s father, Prince Charles, announced his son’s engagement to Markle via a tweet from Clarence House.

Nicholl said that while researching for her book, she was surprised by “the ordinariness” of the couple’s courtship. And when it came to spending time with Markle, Harry was willing to travel from the palace to Toronto, where the Hollywood star filmed “Suits.”

“I was told by one of their friends that Harry would travel to Toronto in those early weeks of their courtship with just one protection officer, in a baseball cap, dressed down, looking absolutely ordinary, not always flying in first-class,” said Nicholl. “He deliberately entered out those journeys to Meghan being as normal as possible, and then some days he’d go to her house and come out with friends. They were seen in Meghan’s neighborhood all before it was public knowledge that they were a couple.”

Not only did Harry fall head over heels for the star, but Markle soon found herself in London.

NUKU'ALOFA, TONGA - OCTOBER 25: (UK OUT FOR 28 DAYS) Meghan, Duchess of Sussex arrives at Nuku'alofa airport on October 25, 2018 in Nuku'alofa, Tonga. The Duke and Duchess of Sussex are on their official 16-day Autumn tour visiting cities in Australia, Fiji, Tonga and New Zealand. (Photo by Pool/Samir Hussein/WireImage)

Prince Harry visited Meghan Markle in Toronto while she filmed "Suits." (Getty)

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“Everything moved quickly,” said Nicholl in a previous interview back in 2018, before the wedding. “According to sources I spoke to, they’ve both settled at Nottingham Cottage. She had her clothes and many of her belongings shipped over [from Toronto]…. They’ve managed to do that all very quietly and very below the radar.”

In October of last year, Markle and Harry revealed to the world they were expecting — an announcement Nicholl wasn’t shocked by.

“As soon as they were married, they wanted to start trying for a family,” Nicholl claimed. “They were both apparently surprised and delighted that it happened as quickly as it did. … Anyone that has seen Harry with children knows there is a magnetism there… He has this incredible ability to connect. He has real empathy for them. He’s simply brilliant with kids and, I think, will be a brilliant father. I know it’s something he’s wanted for a long time.”

Meghan Markle LONDON, ENGLAND - DECEMBER 10: Meghan, Duchess of Sussex on stage during The Fashion Awards 2018 In Partnership With Swarovski at Royal Albert Hall on December 10, 2018 in London, England. (Photo by Tristan Fewings/BFC/Getty Images)

Meghan Markle, Duchess of Sussex onstage during The Fashion Awards 2018 In Partnership With Swarovski at Royal Albert Hall on December 10, 2018, in London, England. (Getty)

Before the baby’s arrival, Markle and Harry moved into their newly renovated Frogmore Cottage on Queen Elizabeth II’s Windsor Estate. Nicholl said it is the ideal setting for the family looking for privacy.

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It’s also a place Harry and Markle will allegedly use to raise a large family.

“I think Harry and Meghan are united in wanting a big family,” said Nicholl. “I think that Frogmore [having] 10 bedrooms is probably an indication that they’re certainly hoping for more than one child. Certainly, from the sources that I spoke to, it’s on the agenda and they don’t want to waste any time about it.”

Meghan, Duchess of Sussex, and Britain's Prince Harry watch a musical performance at Canada House, during an event to mark Commonwealth Day, in central London, on March 11, 2019.  (CHRIS JACKSON/AFP/Getty Images)

After their engagement announcement, Harry told the BBC he was “beautifully surprised” when he first met Markle for the first time. That night led to a five-day camping trip to Botswana three to four weeks later where they got to know each other. Harry said he felt like the “stars were aligned.”

"The fact that I fell in love with Meghan so incredibly quickly was confirmation to me that all the stars were aligned," Harry told the BBC. "This beautiful woman just tripped and fell into my life, I fell into her life. I know that she will be unbelievably good at the job part of it as well."

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Harry also spoke about his late mother Princess Diana and how she would be “over the moon, jumping up and down” knowing he was engaged to Markle. The future royal also has “something old” added to her engagement ring, designed by Harry himself — two diamonds from Diana’s jewelry collection. The center stone is from Botswana, where they camped early in their relationship.

Britain’s Prince Harry and his wife Meghan ride a horse-drawn carriage after their wedding ceremony at St George’s Chapel in Windsor Castle in Windsor, Britain, May 19, 2018. Benoit Tessier:

Millions in the U.S. tuned in to watch Prince Harry and Meghan Markle tie the knot. (Reuters)

"The ring is — is obviously yellow gold because that's... her favorite and the main stone itself I sourced from Botswana and the — the little diamonds either side are from my mother's jewelry collection to make sure that she's with us on this — on this crazy journey together."

"It's days like this I really miss having her around," he said.

"Not being able to meet his mother, it's so important to me to know that she's a part of this with us," Markle also said.

Fox News’ Katherine Lam contributed to this report.