The close relationship between President-elect Donald Trump and his children, particularly his oldest daughter Ivanka and her husband Jared Kushner, has raised questions over what role they'll take on in a Trump administration. Particularly at issue is how they could run his business empire at the same time as he's president — something Trump has said on numerous occasions that they'll do.

And this is a case where existing law is of little help in determining what's actually allowed.

Just after Trump won the election, his legal team claimed that the Trump Organization would be placed in the hands of his oldest children. However, this was almost immediately undercut by Trump naming them to his transition team, with little apparent work being done to move the business over to their control.

Since then, stories have emerged about the three oldest children and Kushner requesting security clearances, as well as Ivanka sitting in on a meeting with the Prime Minister of Japan and on a call with the President of Argentina.

Much of this has been denied by the Trump campaign, and the president-elect's staff has dismissed conflict of interest issues. Meanwhile, all that's clear is that existing laws don't provide much guidance on whether this is appropriate or not.

In 1967, President Lyndon Johnson signed an anti-nepotism bill that says a "public official," designated as the president or a member of Congress, may not:

appoint, employ, promote, advance, or advocate for appointment, employment, promotion, or advancement, in or to a civilian position in the agency in which he is serving or over which he exercises jurisdiction or control any individual who is a relative of the public official.

The law was a response to President John F. Kennedy naming his brother, Robert, to the position of Attorney General, despite him being just 35 and having limited experience as a lawyer. Johnson and Robert Kennedy detested each other, and it's widely believed that Johnson requested the anti-nepotism provision be tacked on to an unrelated bill to spite Robert and possibly damage his presidential run the next year.

The letter of the law, then, prevents President-elect Trump from nominating his children for a cabinet secretary position or other supervisory role. But does it prevent them from working in the White House at all, such as in an unpaid advisory role?

The law has rarely been tested. It did prevent President Jimmy Carter from giving his son a White House internship. Yet a 1993 case resulted in a finding that the law likely wasn't meant to cover staff in the White House or in the Executive Office of the President, only cabinet positions. That suit was filed by a health insurance industry lobbying group after President Bill Clinton appointed Hillary Clinton to chair the Task Force on National Health Care Reform, an action found to not violate the anti-nepotism statute.

There is also precedent for a president's adult family working in the White House under special circumstances, though all these instances took place before the 1967 law.

• Dwight Eisenhower's son, John, a lieutenant colonel in the Army, served as a national security advisor to his father, but this was a military position not appointed by the president.
• Franklin Roosevelt's son, James, served in a variety of roles in his father's White House, culminating in his appointment as Secretary to the President from 1937 to 1938.
• Roosevelt's daughter, Anna, also briefly served as her father's personal assistant near the end of his life, an unofficial position that caused consternation among military officials who didn't know what she was allowed to hear.
• And most famously, Woodrow Wilson's wife, Edith, essentially became the de facto president in October 1919 after Woodrow's devastating stroke incapacitated him and she took over running the White House until March 1921. Such an arrangement would never occur today because of the Twenty-Fifth Amendment, which spells out a formal chain of succession.

None of these are an exact analogy for the possibility of the Trump children working in the White House. It might be legally possible for Kushner to serve as an unpaid advisor if he has no role with Trump's business empire, but this seems unlikely if his wife is helping run it.

Whatever the outcome, it's clear that the Trump family's ambition is rubbing up against the limits of what the law allows. With the president in their corner, they may ultimately carve out unprecedented roles for themselves in forging the relationship between the Trump White House and the Trump Organization.