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01/09/2018 13:30 EST | Updated 01/09/2018 13:33 EST

Kate Middleton Is 36, But Her Love Story With Prince William Is Timeless

These photos will make you believe in happily ever after.

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Prince William and the Duchess of Cambridge attend the Calgary Stampede on July 8, 2011.

Happy birthday, Kate Middleton!

The Duchess of Cambridge turned 36 on Jan. 9, and she's never had more to celebrate: a third baby on the way in April, six years of marriage with Prince William (who she's reportedly always crushed on), a new sister-in-law about to join the family, her work with mental health charities, which has been nothing short of inspiring, and she's about to head off on a royal tour of Norway and Sweden.

Plus there's the fact that she never seems to age, her hair remains remarkably full even after giving birth to two children, and she manages to look poised and regal when most other pregnant moms would be rocking leggings, a greasy top knot, and carrying a bag of chips.

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The Duchess of Cambridge leaves the Christmas Day morning church service at St Mary Magdalene Church in Sandringham, Norfolk.

The duchess is reportedly celebrating her 36th birthday with a "low-key," alcohol-free (she is pregnant, after all) party with eight close friends, a source revealed to the Daily Star Online. Although there is plenty of speculation about who made the guest list, one attendee is a sure pick: her husband, Prince William.

Despite what started as a "roller coaster romance" (they were on-again, off-again, when they first started dating), this royal couple has never seemed stronger.

To celebrate her special day, here's a look back at how far the Duke and Duchess of Cambridge have come since they were fresh-faced students at the University of St Andrews in Scotland.

2003: Romance blooms

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Kate Middleton and Prince William on the day of their graduation ceremony at University of St Andrew's on June 23, 2005.

The duchess and Prince William fell in love at University of St Andrews, where they were both studying art history. They started out as friends, according to Vogue.

The pair moved into a house with two other friends in 2002 (they were still just friends at that point), but things heated up in 2003 after Kate broke up with her boyfriend, according to Cosmopolitan. Their relationship became public after they were pictured skiing together in Klosters, Switzerland, and by 2005 they seemed fully in love at their graduation ceremony, pictured above.

2006-2008: Ups and downs

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Prince William and Kate Middleton after his graduation ceremony at RAF Cranwell on April 11, 2008 in Cranwell, England.

Rumors started swirling that they were in it for the long haul when Kate showed up to watch William graduate as an army officer from Sandhurst military academy in 2006.

"It was the most high-profile public event Miss Middleton has attended as a guest of the prince since they met at St Andrews University," The Telegraph wrote at the time.

"Thus it was one that is sure to fuel speculation that an engagement announcement may not be too far off."

But alas, in 2007, the couple parted ways because Kate wanted to settle down but William wasn't ready, according to Woman magazine. Just months later, they got back together and, in 2008, as William received the wings that made him an RAF pilot, Kate was once again by his side.

2010: William pops the question

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Prince William and Kate Middleton during a photocall to announce their engagement.

Oh, happy day! In November 2010, Kate and William announced their engagement.

In a BBC News interview, William revealed that he popped the question during a trip to Kenya.

"We had a little private time away together with some friends and I just decided that it was the right time, really," Us magazine reported of the interview. "We had been talking about marriage for a while so it wasn't a massively big surprise."

Kate's brilliant 12-carat blue sapphire engagement ring had once belonged to William's mother, the late Princess Diana.

2011: A fairy tale royal wedding and tour

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Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge on their wedding day.

An estimated 2 billion people around the world tuned in to watch Kate and William (who from this point were known as the Duchess and Duke of Cambridge) tie the knot at Westminster Abbey on April 29, 2011.

The duchess' custom Alexander McQueen wedding dress is now known as one of the most famous wedding dresses of all time (and is still inspiring the classic cuts, long sleeves, and lace detailing seen on runway dresses today, according to Brides magazine).

Samir Hussein/WireImage
The Duke and Duchess of Cambridge attend the Calgary Stampede on day 9 of the royal couple's tour of North America on July 8, 2011.

They later went on their first royal tour together, and it was to Canada! There, they visited the Calgary Stampede and even pulled off matching cowboy hats.

2012: There's a baby on the way!

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The duke and duchess leave the King Edward VII Hospital after she was treated for acute morning sickness on Dec. 6, 2012 in London.

In December 2012, they couldn't keep a lid on the news any longer: the royal couple were expecting their first child. Due to acute morning sickness, the duchess was admitted into hospital in her first trimester, which meant they had to announce the pregnancy earlier than planned.

2013: And baby makes three

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The duke and duchess depart The Lindo Wing with their newborn son at St Mary's Hospital on July 23, 2013.

On July 22, 2013, an heir was born. Prince George of Cambridge — the third in line to the crown — was born at 4:24 p.m. and weighed 8 lbs 6 oz.

The duke and duchess beamed as they left the hospital with their new bundle, and Kate made headlines for wearing a Jenny Packham dress reminiscent of what Princess Diana wore after giving birth to William.

2015: It's a girl!

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The duke and duchess show off Princess Charlotte.

On May 2, 2015, the royal couple added another member to their family with the birth of Princess Charlotte of Cambridge.

"It's very special having a new little girl... I feel very, very lucky that George has got a little sister," the duchess later told ITV.

2016: First royal tour as a family of four

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The family on the final day of their Royal Tour of Canada on Oct. 1, 2016 in Victoria.

For their first royal tour as a family of four in September 2016, the royal couple once again chose Canada (we're feeling pretty special right now, actually) as their destination, this time focusing on the West Coast.

Among many official stops, William and Kate made time to attend a children's party at Government House in Victoria, where Princess Charlotte was adorably excited by the balloons.

2017: MORE BABIES

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Catherine, Duchess of Cambridge attends the Charities Forum Event at Paddington Station on Oct. 16, 2017.

Omg it's happening again! In Sept. 2017, Kensington Palace revealed that the Duke and Duchess of Cambridge are expecting their third child.

The baby is due in April.

The Duchess' 36th year is certainly shaping up to be an exciting one.

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