United States First Lady Melania Trump has thanked former first daughter Chelsea Clinton for standing up for her son.
Ms Clinton tweeted support for Barron Trump, 11, after a news site criticised his dress sense.
Mrs Trump replied via Twitter: “Thank you @ChelseaClinton – so important to support all of our children in being themselves!”
Monday’s Daily Caller headline read: “It’s High Time Barron Trump Starts Dressing Like He’s In the White House.”
Many others on social media said they felt the piece was inappropriate.
“As with all previous administrations, we ask that the media give Barron his privacy,” Stephanie Grisham, a spokeswoman for Mrs Trump, told the Associated Press.
“He is a minor child and deserves every opportunity to have a private childhood.”
Ms Clinton, who lived in the White House when her father was US president in the 90s, tweeted: “It’s high time the media & everyone leave Barron Trump alone & let him have the private childhood he deserves.”
She also replied to someone who shared the piece: “No child should be talked about in the below manner-in real life or online. And for an adult to do so? For shame.”
Reporter Ford Springer had written: “Barron was returning to the White House from New Jersey on Sunday and while the president and first lady travelled in their Sunday best, young Barron looked like he was hopping on Air Force One for a trip to the movie theatre.”
Editorial director for conservative The Daily Caller site, Vince Coglianese, defended the writer in an email, according to the Associated Press.
He called it “bro-to-bro advice” and said Mr Springer was “just looking out for the kid”. He is “the most pro-Barron Trump writer I’ve ever met,” he added.
Ms Clinton had previously defended Barron from criticism and cruel jokes, including one tweet that caused a writer for Saturday Night Live to be fired.
Donald Trump repeatedly attacked her mother, Hillary Clinton, when she stood against him in the 2016 president elections, calling her “crooked Hillary”.
Mrs Trump has also spoken out against bullying children in the past.