During his daily news conference on the novel coronavirus, New York Gov. Andrew M. Cuomo (D) offered some familiar advice, again encouraging people to remain indoors, wear masks and stay positive as the state continues to battle a brutal outbreak that has killed more than 18,000 people there.

But then, he suddenly shifted to an easier tone, issuing some unsolicited advice to the dads among his constituents.

It was Sunday, Cuomo said, which meant a spaghetti-and-meatballs feast for his Italian American family. His daughter, 25-year-old Mariah Kennedy Cuomo, had joined him to share updated numbers of cases and covid-19-linked deaths, and had decided to bring her boyfriend to the family meal afterward.

“Advice to fathers: The answer on what you think of the boyfriend is always, ‘I like the boyfriend,’ ” Cuomo said. “Otherwise it triggers ‘NDS.’ NDS is ‘natural defiance syndrome.’ It’s not documented, but it is a psychological condition where if you say as a father ‘I don’t like him,’ natural defiance syndrome kicks in and then they like the boyfriend more because he is opposed by the father. So the answer has to be ‘I like the boyfriend.’ ”

The dad joke went on for more than a minute, as Cuomo reiterated the dangers of showing disapproval for a daughter’s suitor. Better to feign acceptance and eat pasta in peace.

But Cuomo reassured everyone watching at home, and his daughter sitting a few feet away, that he really does appreciate Mariah’s boyfriend. Over the weekend, the three took a walk with Cuomo’s puppy, a shepherd-Siberian-malamute mix named Captain, according to a photo posted to her Instagram.

“The boyfriend is very nice,” he said during the news conference, “and we like the boyfriend.”

Indeed, what’s not to like? A former college football player at Brown University, 29-year-old Tellef Lundevall had a brief professional basketball career in Norway and now runs his own digital media consultancy in Chicago. He’s tall — 6-foot-4, to be exact — and he sails, and did we mention the Norwegian part? (The Post’s attempts to reach Lundevall on Sunday evening were unsuccessful.)

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Walking Captain with the “love gov”

A post shared by Mariah Kennedy Cuomo (@mariahkennedycuomo) on

Cuomo, however, was less positive about his cooking skills. Although he had left tomato sauce bubbling on the stove during the update, he didn’t expect his hard work in the kitchen to win him much favor with his daughters.

“They won’t eat the spaghetti and the meatballs,” he said, “because when I cook it they just won’t eat it. But they move it around the dish and that’s all I can ask.”

The lighter moment came in the middle of yet another sobering breakdown of the novel coronavirus’s impact in the state. More than 18,000 people have died in New York and 248,417 cases have been reported in the state as of Monday morning. But the outbreak appears to be improving. Cuomo announced a new low in the number of coronavirus-related deaths and hospitalizations, after days of leveling off at the state’s peak numbers.

“If the data holds, and if this trend holds, we are past the high point,” he said, “and all indications at this point are that we are on the descent.”

Many people were more interested in Cuomo’s dinner plans than the latest coronavirus numbers. Later in the evening, the governor shared a photo of his family sitting around a table for spaghetti and meatballs. (Contrary to his earlier statements, most of the plates were, in fact, clean, with little tomato sauce left over.)

It was, tweeted a physician, “the most normal thing I’ve seen on TV in weeks.”

Although the concept of “reactance” — wanting something that has been forbidden — is real, a psychologist told The Post that parental disapproval is unlikely to drive two lovers closer together for long. And the real influence may not be defiance, but a preference for the approval of friends.

“It might seem like your children are deliberately defying your wishes, but it’s more likely that they are irritated by your disapproval and care more about what their friends think than what you think,” Gwendolyn Seidman, associate professor of psychology and chair of Albright College’s psychology department, told The Post. “But if parents are less influential than peers, expressing disapproval of your child’s relationships may be more likely to harm your relationship with your child than to actually get your child to break off the romance.”

So, Cuomo’s advice for dads may still keep the peace at his family’s Sunday night spaghetti dinners.