Vice President Joe Biden officiated his first wedding ever -- and it was for a same sex couple. 
 
 Biden officiated over the wedding of two longtime White House staffers, Brian Mosteller and Joe Mahshie, at the Naval Observatory on Monday, his office said. 
 
 Posting a photo of the ceremony on Twitter, Biden wrote, "Proud to marry Brian and Joe at my house. Couldn't be happier, two longtime White House staffers, two great guys." 
 
 Proud to marry Brian and Joe at my house. Couldn't be happier, two longtime White House staffers, two great guys. pic.twitter.com/0om1PT7bKh — Vice President Biden (@VP) August 1, 2016 
 
 His office said the vice president obtained a temporary certification from the District of Columbia to preside over the wedding ceremony, which was attended only by the grooms' families. 
 
 Biden's wife, Jill, later tweeted: "Love is love!" 
 
 The Vice President publicly endorsed same sex marriage in 2012. 
 
 ABC News' Arlette Saenz contributed to this report. ||||| FILE - In this Jan. 20, 2009, file photo, Barack Obama, left, takes the oath of office from Chief Justice John Roberts, not seen, as his wife Michelle, holds the Lincoln Bible and daughters Sasha, right... (Associated Press) 
 
 Formally embarking on his second term, President Barack Obama will take the oath of office Sunday surrounded by family in an intimate inauguration at the White House, 24 hours before re-enacting the ceremony before an excited crowd of hundreds of thousands outdoors at the Capitol. 
 
 The subdued swearing-in is a function of the calendar and the Constitution, which says presidents automatically begin their new terms at noon on Jan. 20. Because that date fell this year on a Sunday _ a day on which inaugural ceremonies historically are not held _ organizers scheduled a second, public swearing-in for Monday. 
 
 A crowd of up to 800,000 people is expected to gather on the National Mall to witness that event, which will take place on the Capitol's red, white and blue bunting-draped west front. Supreme Court Chief Justice John Roberts, who famously flubbed the oath of office that Obama took in 2009, will swear the president in both days. 
 
 Vice President Joe Biden will also be sworn in Sunday in a small, early morning ceremony at the Naval Observatory, his official residence. Justice Sonia Sotomayor, who was appointed by Obama during his first term, will administer the oath of office to the vice president. 
 
 Once the celebrations are over, Obama will plunge into a second-term agenda still dominated by the economy, which slowly churned out of recession during his first four years in office. The president will also seek to cement his legacy with sweeping domestic changes, pledging to achieve both an immigration overhaul and stricter gun laws despite opposition from a divided Congress. 
 
 But for one weekend at least, Washington was putting politics aside. Obama called the nation's inaugural traditions "a symbol of how our democracy works and how we peacefully transfer power." 
 
 "But it should also be an affirmation that we're all in this together," he said Saturday, as he opened a weekend of inaugural activities at a Washington elementary school. 
 
 Only a small group of family members is expected to attend Obama's Sunday swearing-in, including first lady Michelle Obama and daughters Malia and Sasha. A small group of reporters will also be in the room to witness the event. 
 
 Roberts will administer the oath of office shortly before noon in the White House Blue Room, an oval space with majestic views of the South Lawn and the Washington Monument. Named for the color of the drapes, upholstery and carpet, the Blue Room is not typically used for ceremonies and instead has primarily been a reception room as well as the site of the only presidential wedding held in the White House, between then-President Grover Cleveland and Frances Folsum in 1886. 
 
 Later Sunday, Obama and Biden will speak at an inaugural reception attended by supporters. 
 
 But the president will save his most expansive remarks for Monday, when he delivers his second inaugural address to the crowd gathered on the Mall and millions more watching across the country and the world. Obama started working on the speech in early December and was still tinkering with it into the weekend, aides said. 
 
 The president's address will set the stage for the policy objectives he seeks to achieve in his second term, including speeding up the economic recovery, passing comprehensive immigration and gun control measures and ending the war in Afghanistan. However, aides said Obama would save the specifics of those agenda items for his Feb. 12 State of the Union address. 
 
 The president launched a weekend of inaugural activities Saturday by heading up a National Day of Service. Along with his family, Obama helped hundreds of volunteers spruce up a Washington area elementary school. 
 
 His shirt sleeves rolled up, Obama donned a pair of rubber gloves, picked up a paint brush and helped volunteers stain a bookshelf. 
 
 Obama added the service event to the inaugural schedule in 2009 and is hoping it becomes a tradition followed for future presidents. 
 
 Mrs. Obama, speaking to volunteers Sunday, espoused the importance of giving back in the midst of the weekend of pomp, circumstance and celebration. 
 
 "The reason why we're here, why we're standing here, why we're able to celebrate this weekend is because a lot of people worked hard and supported us, and we've got a job to do and this is a symbol of the kind of work that we need to be doing the next four years," Michelle Obama said at Burrville Elementary. 
 
 ___ 
 
 Follow Julie Pace at http://twitter.com/jpaceDC ||||| President Barack Obama tweets his first tweet from his new @POTUS account from the Oval Office, May 18, 2015. (Official White House Photo by Lawrence Jackson) 
 
 Today, with a tweet from the Oval Office, President Obama launched @POTUS, the official Twitter account of the President of the United States. 
 
 Hello, Twitter! It's Barack. Really! Six years in, they're finally giving me my own account. — President Obama (@POTUS) May 18, 2015 
 
 The @POTUS Twitter account will serve as a new way for President Obama to engage directly with the American people, with tweets coming exclusively from him. President Obama is committed to making his Administration the most open and participatory in history, and @POTUS will give Americans a new venue to engage on the issues that matter most to them. 
 
 Looking for more ways to engage with the White House on Twitter? Be sure to check out all of our official accounts: 
 
 The White House: @WhiteHouse 
 
 Vice President Joe Biden: @VP 
 
 First Lady Michelle Obama: @FLOTUS 
 
 Dr. Jill Biden: @DrBiden 
 
 Live coverage from the White House: @WHLive 
 
 Press Secretary Josh Earnest: @PressSec 
 
 Senior Advisor Valerie Jarrett: @VJ44 
 
 Communications Director Jen Psaki: @Psaki44 
 
 White House updates in Spanish: @LaCasaBlanca 
 
 Chief Official White House Photographer: @PeteSouza 
 
 You can find a full list of official White House Twitter accounts here.
– The wedding of two White House staffers was extra special Monday, and not just because the vice president was in attendance. Joe Biden was actually the one to pronounce the couple husband and husband as he officiated his first ever wedding, reports ABC News. The couple—Brian Mosteller, the director of Oval Office operations, and Joe Mahshie, Michelle Obama's trip coordinator—specifically requested him, reports BuzzFeed. "Proud to marry Brian and Joe at my house. Couldn't be happier, two longtime White House staffers, two great guys" Biden tweeted alongside a photo of the ceremony. The wedding took place at the VP residence at 4pm, with only family present.