And now for a question of grave national importance: Why does “Saturday Night Live” think Eric Trump is the dumb one?

For a year now, SNL has ­portrayed the elder Trump brothers, Eric and Don Jr., as a study in contrasts: Don is the adult and his younger brother is still very much a child — and perhaps a somewhat delayed one at that. It’s like something out of Steinbeck, with Don placating Eric with toys, treats and reassuring words.

In a bit on the show this month, SNL’s “Weekend Update” co-host Colin Jost asked the characters what they’d been up to recently.

“I took a trip to India, which is an in­cred­ibly poor country, where I’m hoping to make a lot of money,” said Don Jr., as played by Mikey Day.

“I saw ‘Paddington 2’!” said Eric, played by Alex Moffat with the tone of a 5-year-old.

In reality, Donald Trump Jr. is a 40-year-old father of five and a graduate of the University of Pennsylvania’s Wharton School, and Eric is 34, a new father and a graduate of Georgetown University. They are executive vice presidents of the Trump Organization. They are essentially running the family business while their father runs the country.

None of this matters in the eyes of partisans and satirists. After 25 years of young daughters in the White House, America finally has a first family with grown men to pick on. And the Trump brothers, as swaggering, slick-haired trustees of real estate and reality TV wealth, would seem perfect for a ribbing, however imprecise, on SNL.

“Unfortunately it is the price one pays for being in a political family,” Eric says, via email, about the characterization. “They got it wrong, they detest us and they will do anything to try and undermine our credibility.”

Writers for “Saturday Night Live” were not available to ­discuss why they chose to play the brothers as mental opposites. I interviewed the brothers separately for an hour each in April 2016, before their father locked up the Republican nomination, and before the campaign and family were under scrutiny for strange contacts with the Russians.

“What’s the difference between you and Eric, besides your age?” I asked Don Jr., who replied with a “huh.” He appeared stumped. So I said, after a long pause: “I know you’re very close . . .”

“Yeah, we are,” Don Jr. said. “We’re — I don’t know. We certainly are different. I’m probably a little more relaxed about certain things. . . . There are times he gets a little more formal, where I’m sort of almost always informal.”

For our interviews, Eric sat behind a desk in a suit, with cuff links from Tiffany & Co., and Don Jr. sat in front of the desk in jeans and hiking shoes. Eric came across as more measured and less excitable than his brother, whose slick black hair and urgent cadence can be unnervingly intense. “Saturday Night Live” does not capture either of them in the slightest. Then again, the show has never gotten Hillary Clinton right, either.

“Down-to-earth, remarkable kids,” an assistant headmaster for their alma mater, the Hill School, told me then.

Eric is “quiet” and “humble,” one of his Georgetown classmates told me.

One modern difference is clear: Don Jr. has been in the fray a lot more than Eric over the past two years. It was Don Jr. whom WikiLeaks targeted in a series of direct messages on Twitter. It was Don Jr. who had that funny meeting with the Russians in Trump Tower in June 2016, after being promised incriminating information on Clinton. It was Don Jr. who then tweeted out emails intended to preempt a New York Times exposé but which only raised more suspicions, inspiring pundits to expound on his apparent naivete.

“I’d like to apologize to Eric Trump,” Stephen Colbert said on his late-night show last July. “We always thought you were the dumb one. We were wrong.”

“Apologies to Eric, But There’s a New Dumbest Trump,” was the headline on a November piece by Charles P. Pierce in Esquire.

In 2006, the New York Daily News labeled Eric “the quiet Trump.” He’s also the tallest Trump, at 6-foot-5. Is he the dumbest? Who can say. Michael Wolff’s muckraking book “Fire and Fury” describes the Trump brothers as having an “infantile relationship to their father,” who regularly pointed out “that they were in the back of the room when God handed out brains.” Ivanka Trump, Wolff wrote, was “the designated family smart person.”

When a whole family enters politics, as the Trumps have done, its siblings undergo a public sorting. The media try to sniff out black sheep. Quirks and idiosyncrasies balloon into defining traits. Before his brothers were killed, Ted Kennedy was the third wheel — a rude, ruddy bon vivant in contrast to the austere Bobby and polished Jack. It took Ted years to varnish his reputation into “the lion of the Senate.”

Billy Carter, brother of the upstanding Jimmy, had a beer named after him. He once admitted to being “the world’s most public drunk,” and was investigated by the Justice Department after he got cozy with Moammar Gaddafi.

Michael and Ronald P. Reagan were 35 and 22, respectively, when their father was inaugurated. They have different mothers and different mind-sets. Michael has defended President Trump and implied that Ron didn’t even vote for their father; Ron, an outspoken liberal, has called Trump “a deeply damaged human being.”

Introverted Jeb was once viewed as the heir apparent to George H.W. Bush, but then his older brother, George W. — formerly a rakish frat boy who drank too much — turned his life around and became president. Against Trump in 2016, Jeb’s strait-lacedness turned into a straitjacket.

The Clintons had to tolerate sibling liabilities. Hugh and Tony Rodham were circus clowns ­compared with their temperate older sister, Hillary; they got tangled up in murky business and legal dealings, and were used by Clinton enemies to tarnish the first lady. Bar band lead singer Roger Clinton, meanwhile, got a short-lived record deal out of his family’s rise to fame — and later, a pardon from his half brother Bill for his 1985 cocaine-dealing conviction.

In the first year of their father’s presidency, 19-year-old twins Jenna and Barbara Bush were both cited for underage drinking, though Jenna earned a rowdier reputation. Last year, conservative media feasted on photos and video of Malia Obama partying at Lollapalooza and smoking at Harvard; liberals responded by juxtaposing this evidence against photos of the Trump brothers hoisting big-game carcasses in Africa.

Politics turns siblings into punchlines, even when reality isn’t very funny. Don Jr., who routinely retweets promoters of the bonkers Pizzagate conspiracy theory, was called to testify before the House Intelligence Committee. Both he and Eric are spending a good deal of time defending their father from relentless attacks, both humorous and political.

“I’m saving dying children,” Eric told The Washington Post in 2016, amid inquiries about his charity making a payment to a Trump golf course. “We do tremendous good for people. And you’re sitting there tearing us apart.”