Elon Musk’s younger brother, Kimbal, took to X on Monday to lambaste President Trump’s tariffs, calling them a “structural, permanent tax on the American consumer.” He also said Trump appears to be the “most high tax American President in generations.”

“Even if he is successful in bringing jobs on shore through the tariff tax, prices will remain high and the tax on consumption will remain the form of higher prices because we are simply not as good at making things,” Kimbal Musk wrote on social network X, one the companies in his brother’s extensive portfolio.

The younger Musk owns a restaurant chain called The Kitchen, is a board member at Tesla, and former director at SpaceX and Chipotle. He has also co-founded and invested in other food and tech startups, including Square Roots, an indoor farming company, and Nova Sky Stories, a creator of drone light shows that he bought from Intel.

Elon Musk is a top adviser to Trump, overseeing the Department of Government Efficiency (DOGE), an effort to drastically cut federal spending, largely through layoffs, and consolidate or eliminate agencies and regulations. However, his relationship with some key figures in the Trump administration has been showing signs of strain in recent days as the president’s sweeping tariffs have led to a dramatic selloff in stocks, including for Tesla, which is down 42% this year and just wrapped up its worst quarter since 2022.

Over the weekend, Elon Musk took aim at Trump trade adviser Peter Navarro, disparaging his qualifications in a post on X.

“A PhD in Econ from Harvard is a bad thing, not a good thing,” Musk wrote, after Navarro told CNN on Saturday that, “The market will find a bottom” and that the Dow will “hit 50,000 during Trump’s term.” It’s currently at about 38,200.

Musk also said that Navarro hasn’t built “s–t.” Navarro told CNBC on Monday that Musk is, “not a car manufacturer” but rather a “car assembler,” dependent on parts from Japan, China and Taiwan.

Tesla was seeking a more moderate approach to trade and tariffs in a recent letter to the U.S. Trade Representative.

According to Federal Election Commission filings, Kimbal Musk this year has contributed funds to the Libertarian National Committee and Libertarian Party of Connecticut. Last year, while his brother became the biggest financial backer and promoter of Trump, Kimbal donated to Unite America PAC, a group that markets itself as a “a philanthropic venture fund that invests in nonpartisan election reform to foster a more representative and functional government.”

A representative for Kimbal Musk didn’t immediately respond to a request for comment.

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