WASHINGTON — First son Barron Trump was “very respectable” when he crossed paths with former President Joe Biden at the Capitol Rotunda for his father’s inauguration in January, according to his older brother Eric. During the inauguration, the hulking Trump scion had approached Biden, 82, and shook hands with him before leaning in and muttering something mysterious to the outgoing leader — sending the internet aflutter with speculation. TV cameras captured the viral moment, but it had long been unknown what Barron, 19, actually said to Biden.

“But like, ‘Congratulations, and best of luck to you,’ or something like that. Something very respectable,” Eric revealed.

Theories had swirled on social media that Barron had snapped at his father’s predecessor, with a clip showing Biden’s smile suddenly dropping after the interaction.

Eric, who said he’s very close to Barron, mused about how lip readers had thoroughly analyzed the encounter.

The elder Trump scion recalled how PBD Podcast host Patrick Bet-David asked him whether his younger brother had used the F-bomb against the 46th president during their encounter.

“Patrick Bet-David, I was on his show and he goes, ‘Did Barron really tell Biden to go f himself?’ He [Barron] just doesn’t have that in him,” the Trump organization executive recounted.

“He’s probably thinking it, he definitely has it up here, but like he’s too courteous to actually go out there and say it,” he added.

Eric’s revelation about Barron’s small talk with Biden came while riffing about who the nicest Trump is.

“I’m the nicest Trump,” Eric said to laughs from the audience during his interview with Kelly on her tour.

He then acknowledged that his half-sister, Tiffany, might be the nicest Trump. Kelly implied that he is the nicest of the male Trumps.