It traces back to the Kennedys. After President John F. Kennedy appointed his 35-year-old brother, Robert, as attorney general -- a basically unprecedented move at the time, involving an office for which few thought the younger Kennedy was qualified -- Congress in 1967 passed an anti-nepotism law.

... But it's not completely clear whether this law applies specifically to White House staff. In other words, Kushner certainly couldn't be a Cabinet secretary, but the Trump team seems to think he could be an adviser. And the possible precedent for that traces back to another famous political family: the Clintons.

When President Bill Clinton appointed his wife, Hillary, to head up his health-care efforts, the couple was sued . It wasn't that the filers wanted to nail the Clintons for nepotism, but given that she could not be an official government employee under the law, they argued that the meeting of her health-care task force should be open to the public.

The appeals court decision that resulted [which concluded that Hillary Clinton did not break anti-nepotism laws but that her meetings should be public] might have given Kushner and Trump hope for getting around the law in 2016, though some experts are dubious.