Democratic presidential front-runner Joe Biden first learned from Page Six that his younger son, Hunter, was having an affair with the widow of his late elder son, Beau, according to a new report.

In a tell-all New Yorker interview, the mag reveals that the former vice president didn’t know about the controversial liaison between Hunter and Hallie Biden until Page Six reached out for comment in 2017 — and Hunter begged his dad to issue a statement blessing their relationship.

“I said, ‘Dad, Dad, you have to.’ He said, ‘Hunter, I don’t know if I should. But I’ll do whatever you want me to do,'” he tells the magazine.

“I said, ‘Dad, if people find out, but they think you’re not approving of this, it makes it seem wrong. The kids have to know, Dad, that there’s nothing wrong with this, and the one person who can tell them that is you.'”

Page Six first reported in March 2017 that the still-married Hunter and his sister-in-law, Hallie, had struck up a relationship following Beau’s death in May 2015.

The news came after Hunter’s estranged wife, Kathleen, filed for divorce — claiming in court papers that he was blowing the family’s money on booze, drugs, prostitutes and strippers.

Hunter claimed to the New Yorker that he’d never hired prostitutes and hadn’t been to a strip club in years — but said that after the story was published, “I went directly to a strip club. I said, ‘F–k them.'”