Former President George H.W. Bush joined Twitter on Tuesday and quickly sent a message out about Nelson Mandela. Bush was the only living former president to miss Mandela’s memorial service in Johannesburg, and his first tweet was a message of condolence. Earlier this year, Bush was hospitalized for weeks due to a respiratory infection, and since then he has rarely traveled or attended public events. Bush's son, the 43rd president, traveled along with President Obama to the memorial service, and posted pictures with former President Clinton, former Secretary of State Hillary ClintonHillary Rodham ClintonMaxine Waters: ‘I’ve never seen anybody as disgusting or as disrespectful’ as Trump Samantha Bee roasts Trump at mock correspondents' dinner Dems seeing big increase in midterm House candidates MORE and U2 frontman Bono to his Instagram account. But while Bush has posted to the picture-sharing website, his father beat him to joining Twitter. Instead, George W. Bush is represented on the social network by his presidential library — @BushCenter. Jimmy Carter has followed a similar path, with @CarterCenter tweeting on his behalf. Former President Bill ClintonBill ClintonBuzzFeed toasts free press at alternative WHCA party Why Trump sitting out the correspondents' dinner is a huuuge mistake Larry Summers: Mnuchin squandering his credibility with Trump tax proposal MORE joined Twitter earlier this year at the urging of comedian Stephen Colbert, who during a Clinton Global Initiative panel registered the former president with the user name @PrezBillyJeff. During the appearance, Clinton said he was initially reluctant because he was not sure “I have room on my schedule to tweet.” But, Clinton said, ultimately he saw value in using the social media tool to reach a new audience. A few weeks later, Clinton again appeared on the show to announce that he had adopted the “more dignified” @BillClinton handle.