President-elect Donald Trump's son-in-law, Jared Kushner, will become a senior White House adviser and work on trade deals and the Middle East, transition officials said on Monday, in a rare case of a close presidential family member taking on a major job.

Kushner, 35, who is married to Trump's daughter Ivanka, is taking the job after receiving legal counsel he would not be violating a U.S. anti-nepotism law based on court rulings that the statute does not apply to the White House. The position does not require U.S. Senate confirmation.

Ivanka Trump, who like her husband has been a trusted adviser to the president-elect, will not take on a role in her father's White House but will focus instead on settling her family in Washington.

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Kushner and his wife, Ivanka Trump, pose for a photo at a gala in New York. Donald Trump has publicly praised his son-in-law, saying 'he's very good at politics.' (Evan Agostini/Associated Press)

Both of the Trumps will undertake significant divestments of their wide-ranging financial portfolios as they prepare for their move to Washington from New York and face inevitable questions about a potential conflict of interest.

Kushner emerged as an important voice early in Trump's campaign and was involved in almost every aspect of it, from key personnel decisions to strategy and fundraising.

'We have the better argument'

​Senior transition officials and a lawyer for Kushner laid out the arrangement in a conference call with a small group of reporters.

Kushner is to work closely with incoming White House chief of staff Reince Priebus and senior strategist Steve Bannon in advising the new president. Officials said he would focus, at least in the beginning, on trade policy and the Middle East.

Jamie Gorelick, a New York lawyer who served as deputy attorney general for former president Bill Clinton, helped advise Kushner on whether he would violate a 1967 anti-nepotism statute and said he would not.

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Kushner travelled to Washington with Trump a few days after the election and met with White House Chief of Staff Denis McDonough, right, while U.S. President Barack Obama met with Trump on transition planning in the Oval Office. (Jim Watson/AFP/Getty Images)

"I'm not saying that there isn't an argument on the other side, and I respect the people who have made the argument on the other side. I just think we have the better argument," she said.

Gorelick said Congress in 1978 authorized the president to hire personnel for the White House office "without regard" to federal personnel laws like the anti-nepotism statute, and that the Justice Department had described that authority as unfettered and sweeping.

"Even without that law, two D.C. Circuit decisions strongly suggest that the White House Office is not an 'agency' under the anti-nepotism statute, a position supported by the views of the Justice Department under presidents Bill Clinton and George W. Bush," Gorelick said.

Divestments to come

In order to comply with federal ethics laws and after consulting the Office of Government Ethics, Kushner will take a number of steps to divest substantial assets, Gorelick said.

Kushner will resign from his positions as chief executive of the Kushner Companies and as publisher of the New York Observer newspaper. He will also divest from any interests in the New York Observer, Thrive Capital, 666 Fifth Avenue and any foreign investments.

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Kushner helped with Trump's transition team and is considered an influential member of his inner circle. (Carolyn Kaster/Associated Press)

In addition, Kushner will remove himself from participating in matters that could have a direct effect on his remaining financial interests.

Those interests include real estate in the New York area, Ivanka Trump's interest in the new Trump hotel in Washington and the Ivanka Trump Brand fashion business, the officials said.

Ivanka Trump will not participate in the management or operations of the Trump Organization or the Ivanka Trump brand or fashion business.

She will divest significant assets, including all common stock and resign from all officer and director positions she holds in the Trump Organization.