The 12-year relationship of college sweethearts Mark Zuckerberg and Priscilla Chan

Mark Zuckerberg Priscilla ChanFacebookMark Zuckerberg and a pregnant Priscilla Chan.

Facebook CEO Mark Zuckerberg just announced that he and his wife, Priscilla Chan, are expecting their first child together.

Zuckerberg and Chan are college sweathearts. They tied the knot on May 19, 2012, one day after Facebook’s IPO.

The wedding was a surprise for all of the guests, who thought they were attending a medical school graduation party for Chan.

The couple met in line for the bathroom at a frat party 11 years ago. Now Chan has been dubbed the “first lady” of Facebook, and the pair have been extremely generous with their fortune.

Here’s a summary of their time together, as told through their Facebook timelines.

Priscilla Chan and Mark Zuckerberg met in line for the bathroom at a Harvard party in 2003. Zuckerberg's fraternity, Alpha Epsilon Pi, was hosting a party and Chan, a sophomore from the Boston area, was there.

When Zuckerberg took Chan out the first time, he told her he'd 'rather go on a date with (her) than finish his take-home midterm,' Chan told 'Today's' Savannah Guthrie.

Chan was one of the first people to join Facebook, on Feb. 5, 2004.

Perhaps the most telling sign of their long relationship is that Chan knew Zuckerberg before hoodies were his clothing of choice. 'There is the black fleece period, the red puma period, the short lived white coat period and the really soft green thing period,' she commented in 2006.

Chan loves kids. She worked at FASE and at The Harker School teaching fourth and fifth grade. 'These little ones inspired me,' she says. Chan now works as a pediatrician in San Francisco.

In 2007, Chan graduated from Harvard. Zuckerberg was there to celebrate. Chan followed him to California. She became a med student at UCSF and rented an apartment near Golden Gate Park, where Zuckerberg would visit her most weekends.

'They walk in the park, go rowing (he insists that they go in separate boats and race), play bocce or the board game the Settlers of Catan. Sundays are reserved for Asian cuisine,' The New Yorker writes of the couple.

Source: The New Yorker

Because Zuckerberg is so busy with Facebook, Chan set some strict ground rules for their relationship. Chan requires a minimum of 100 minutes of alone time per week, not at Facebook. She also requires one date per week, TechCrunch reports.

The couple has travelled the world together. They typically spend two weeks in December abroad and they have taken trips to China to see her family. Zuckerberg even started learning Mandarin.

Chan was there through all the ups and downs. Here, she helped Zuckerberg take photos of himself for a BusinessWeek story.

And Chan was there when Zuckerberg turned down multiple buyout offers, including a $1 billion offer from Yahoo in 2006. Chan told The New Yorker she thought that was Zuckerberg's most stressful time period. 'I remember we had a huge conversation over the Yahoo! deal. We try to stick pretty close to what our goals are and what we believe and what we enjoy doing in life -- just simple things,' she says.

Source: The New Yorker

In September 2010, Chan moved in with Zuckerberg. He announced the news on Facebook: 'Priscilla Chan is moving in this weekend. Now we have 2x everything, so if you need any household appliances, dishes, glasses, etc please come by and take them before we give them away.'

One month later they offered hoards of candy to trick or treaters.

In March 2011, Chan and Zuckerberg picked up this pooch, Beast.

Priscilla Chan, Mark Zuckerberg and their dog, Beast.

That same month, the couple finally acknowledged they were in a relationship on Facebook.

In 2012, Zuckerberg and Chan tied the knot just days after Chan graduated from med school and Zuckerberg took his company public.

They honeymooned in Italy but had a pretty casual vacation. They were spotted eating McDonald's for a meal while abroad.

In 2012, they enjoyed a 'budget' vacation in Hawaii, surfing, and feasting on Kauai's Bubba burgers, according to The Daily Mail.

Some have speculated that they were using that vacation to check out some Hawaiian properties -- in October 2014, they purchased a 750-acre property in Kauai for more than $100 million.

The couple also recently finished renovations on a $10 million house they own in the Dolores Heights neighbourhood of San Francisco.

Together, Chan and Zuckerberg have become major donors and have given hundreds of millions to support education on both coasts. Last year, the couple announced they will be putting $120 million toward improving San Francisco public schools.

In February, the couple donated $75 million to the San Francisco General Hospital Foundation. The hospital was renamed the Priscilla and Mark Zuckerberg San Francisco General Hospital and Trauma Center.

Zuckerberg shared in a Facebook post Friday that he and Chan are expecting their first child together, a baby girl. In the post, Zuckerberg revealed that the couple had been trying to get pregnant for some time, and that Chan had suffered three miscarriages. 'It's a lonely experience,' Zuckerberg wrote. 'We hope that sharing our experience will give more people the same hope we felt and will help more people feel comfortable sharing their stories as well.'

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