Kim Jong Un’s half-brother was working as a CIA informant before his broad-daylight assassination in 2017, a report says.

The “nexus” — as one source called it — between the US spy agency and the dictator’s brother, Kim Jong Nam, was revealed Monday by the Wall Street Journal, which cited “a person knowledgeable about the matter.”

Little is known about Kim Jong Nam’s alleged snitching, only that he met with CIA operatives on multiple occasions, the Journal reports.

The North Korean leader’s half-brother had been exiled and living on-and-off in the Chinese enclave of Macau when he began making contact with the CIA and other security services across the world, according to the Journal’s source.

US officials, however, told the newspaper it’s highly unlikely that he knew any top secrets or details about the Hermit Kingdom’s inner workings.

The Journal’s report comes as tensions continue to simmer between the Trump administration and Pyongyang. A February summit in Hanoi that featured both Kim Jong Un and President Trump was the last time the two sides met and talked, but the discussions fell through.

A book that is set to be published on Tuesday by Washington Post Beijing bureau chief Anna Fifield — titled “The Great Successor” — will reportedly outline Kim Jong Nam’s ties to the CIA.

Fifield described his relationship with his brother to The Japan Times over the weekend, and also spoke about their parents and relatives.

“Kim Jong Nam and his cousin, Ri Nam Ok, were like birds in a cage, their movements severely restricted and their life enveloped in paranoia,” explained Fifield. “All of them had to live in varying degrees of secrecy but all of them were allowed to travel and live a good life outside. For some — like Kim Jong Nam’s mother — that was a perk of being in the royal family. But, for others, it must have opened their eyes to an alternative. But what I find most interesting is that many of them are still in some sort of cahoots with the regime. They were in privileged positions and seemed unable to completely let go of the benefits that came with that. Either way, we can see that this is an extremely dysfunctional family.”

According to Fifield, “everyone related to Kim Jong Nam has gone to ground since his assassination.”

“Understandably so,” she told the Japan Times. “The men in this family in particular have reason to fear what might happen to them. The Kim family claims legitimacy in part on its supposed ‘Paektu bloodline’ — the idea that the family descended from the mountain that is the mythical home of the Korean people. Therefore anyone — or rather, in North Korean hierarchy, any man — from this family could theoretically claim the right to the throne and be a threat to Kim Jong Un.”

Nam was murdered on Feb. 13, 2017 at the Kuala Lumpur International Airport in Malaysia. Two women were later arrested for the mid-day killing, which involved them smearing a deadly nerve agent on Nam’s face as he walked through the airport.

One of the women was released from jail last month for good behavior after copping a plea deal that reduced her charges to causing injury. The other was let go back in March.