Donald Trump is “very intent on bringing my brother down”, Joe Biden’s sister said.

“The only race I wasn’t enthusiastic about Joe getting involved in was the 2020 presidency,” Valerie Biden Owens told CBS News.

“Because I expected, and was not disappointed, that it would be ugly and mean, and it would be an attack on my brother, Joe, personally and professionally, because the former president is very intent on bringing my brother down.”

A year and a half into his presidency, Biden is battling crises at home including inflation and the coronavirus pandemic and abroad, over the Russian invasion of Ukraine.

Trump dominates the Republican party, propagating the “big lie” about voter fraud in his defeat by Biden which fueled the January 6 attack on the US Capitol, continuing to attack Biden as incapable of the demands of office, flirting with a third White House run and dispensing endorsements to candidates in the midterm elections.

On Sunday, the Republican House minority leader, Kevin McCarthy, claimed Republicans would not swiftly impeach Biden “for political purposes”, should as expected the party take the House in November.

Biden Owens helped raise her brother’s children after his first wife and daughter were killed in a car crash and has worked on all his campaigns. She has written a book called Growing Up Biden: A Memoir.

“I assumed from the beginning that the former president and his entourage would attack my brother by going and attacking my family,” she said.

Trump has focused on Hunter Biden, the president’s son, who has written his own book about his struggle with addiction and whose business affairs are the subject of scrutiny.

Hunter Biden was one subject of Trump’s attempt to withhold military aid from Ukraine in exchange for political dirt, an attempt that led to Trump’s first impeachment. To Republicans, Hunter Biden remains a tempting target. Federal investigators are known to be looking at his financial affairs.

His aunt told CBS: “There hasn’t been a there, there since it was mentioned in 2019 or whenever it was.”

She also said: “Hunter has written in exquisite detail about his struggle with addiction, his walk through hell, and I am so grateful he has been able to walk out of hell, but I don’t think there’s a family in this country who hasn’t tasted it.”

Trump’s destructive power remains widely feared. Pundits and rivals are watching his endorsements closely, among them a choice to back Mehmet Oz, a TV doctor, for the Senate nomination in Pennsylvania, a pick many Republicans opposed.

On Monday, a possible rival to Trump for the 2024 Republican nomination, Ron DeSantis, was offered a warning that might have sounded familiar to Valerie Biden Owens.

Nikki Fried, a Democrat running to oppose DeSantis for governor in Florida, told Business Insider that if Trump runs again and gets back on Twitter – from which he has been banned since the Capitol attack – “I say one tweet created [DeSantis] and one tweet can destroy him”.