Former Vice President Joe Biden Joe BidenPelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Hillicon Valley: Subpoenas for Facebook, Google and Twitter on the cards | Wray rebuffs mail-in voting conspiracies | Reps. raise mass surveillance concerns Fox News poll: Biden ahead of Trump in Nevada, Pennsylvania and Ohio MORE revealed on Tuesday that his family and former President Obama's family got together last weekend to celebrate the high school graduation of his granddaughter Maisy Biden and of Sasha Obama.

“Her best friend is Sasha Obama. Barack and Jill and the whole family, we had a whole get together," Biden told a crowd in Davenport, Iowa.

Maisy Biden and Sasha Obama graduated from Washington, D.C.'s Sidwell Friends School on Sunday.

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The former vice president cited the graduation as his reason for not attending the Iowa Democratic Party's annual Hall of Fame dinner last week.

“One of my competitors criticized me for not going to Iowa to talk for 5 minutes," Biden told a group of lobbyists and donors in Washington on Monday. "My granddaughter was graduating. It was my daughter’s birthday. I would skip inauguration for that."

While Biden was not present at the event, he appeared to be on the minds of his Democratic primary opponents, who took numerous opportunities to indirectly criticize him over the weekend.

Biden's visit to Iowa on Monday marked his second visit to the Hawkeye State as a 2020 contender.

The visit also coincided with President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE's visit to the state.

The two men criticized each other on Tuesday, with Biden calling Trump "an existential threat to America," and Trump saying the former vice president was "slower than he used to be."