Barron Trump entertained his tiny nephew while his dad, U.S. President Donald Trump, signed documents in the President's Room at the U.S. Capitol building Friday.
The entire family, including Trump's young grandchildren, stood by as the commander-in-chief got to work in front of photographers and television camera-people, following Trump's official swearing-in ceremony and celebratory parade.
Barron, 10, was seen behind his seated father, playing peek-a-boo with his half-sister Ivanka's 9-month-old son, Theodore, Us Weekly said.
CNN video of the interaction also captured Barron giving a "High 5" to the baby as Ivanka and first lady Melania Trump, Barron's mother, look on and smile. The clip has gotten nearly 7 million views on Facebook in less than 24 hours.
Melania and Barron plan to stay at their home in New York City until the end of the school year and are expected to move into the White House with the president in June.