“Jupiter’s Circle” peels off of “Jupiter’s Legacy” to reveal superheroic private lives. (courtesy of Image Comics)

MARK MILLAR’s starry career has spanned creator-owned mega-projects, influential DC and Marvel superhero tales and numerous panel-to-screen hit adaptations (the “Kick-Ass” films, “Wanted,” “Kingsman: Secret Service”), taking the writer from the Scottish bogs to the world stage.

Yet only upon being in the company of “incredibly rich guys” in Hollywood, Millar said, did a certain inspiration strike — a concept that led to his “Jupiter’s Legacy” series for Image Comics. The Glasgow native considered the years of drive and determination that allowed these film financiers and producers to reach their high-stakes echelon.

“These guys are self-made — they have a drive and a focus in their life, because they have to work, whereas [their] children … There’s almost no point in doing four hours of homework every night, because you’re inheriting your dad’s $100-million fortune,” Millar told The Post’s Comic Riffs.

“I actually think that growing up modestly like I did in Scotland, where we had nothing really, was actually an incredible advantage,” continued Millar, who dropped out of college for lack of money when his own father died. “And [the “Jupiter" series] is about that. The idea of being the children of somebody famous is a curse.”

In the world of superhero comics, babies are rarely conceived narratively, if not creatively (Reed Richards’s children and Damian Wayne being some well-known exceptions). Who has time for diapers when you’ve got a planet to save?

Millar admits to creating then-unseen scenarios while writing for Marvel and DC — concepts that he knew would never appear in the pages of a mainstream superhero comic book. But the ideas always stuck with him. What if two of the greatest superheroes had a child?

“Wouldn’t it be so hard to be the son, [or] especially the daughter, of Superman and Wonder Woman?” Millar said. “Where the hell does your life go? Because they’re the greatest people who ever lived.”

In “Jupiter’s Legacy,” Millar tells of Silver Age heroes whose children try to avoid the long shadows of their graying parents’ legacies. And because multiple generations are involved, Millar necessarily deals with aging, too.

“Superman is a fantasy father figure for a reader [of] those books, but the idea of trying to fill those shoes — to try to live up to Superman — would just be almost impossible. It was really fun to play it out with [‘Jupiter’s Legacy’] because comic-book characters are never allowed to grow old. It’s like Bart Simpson. They are perpetually the same age,” said Millar, who was a teenager when his own father died. “And there’s only so many stories you can tell about Doctor Octopus breaking out of prison and robbing a bank. Even the Joker escaping from Arkham Asylum. People just got fed up with seeing those types of stories. I love creating my own universe and owning my own universe.”

Politics and the burden of being super-human spawn are strong themes in “Jupiter’s Legacy.” Millar pits the wits of two superhero brothers — one conservative, the other a liberal interventionist — against each other. It’s the alpha-hero-to-all brother who says that despite being powerful, superheroes must stay out of government and politics; his brother feels that power must be used to fix a system of government that is not working.

“That idea of the world not quite going as it should, and an older man feeling he can come in and do a better job, that’s something that is quite timeless,” Millar said of the dilemma facing his sibling heroes. “That story could have worked 500 years ago. It would have worked in the 1970s with Vietnam and it works now, unfortunately. The world is never quite in a great place. And superheroes are such great metaphors to tell stories with.”

“Jupiter’s Legacy” brings betrayal; a son trying to be the hero his father was but slowly realizing that may never come to be; and a daughter who never wanted to be a hero but realizes her destiny may lie that way.

But before a potential second-generation super-powered sibling rivalry can play out, Millar is giving the readers of “Jupiter’s Legacy” a look into the past with “Jupiter’s Circle,” which will serve as a sort of prequel to the first five issues of “Jupiter’s Legacy.”

“Jupiter’s Circle,” which will debut early next month from Image Comics, is set in the “Mad Men”-esque Silver Age, providing a look at the original heroes of Millar’s “Jupiter” universe in their prime, starting in the late 1950s.

“I love that world — there’s something beautiful about that world. That amazing technicolor,” Millar said. “America to me — remember, I’m a foreign guy — so to me, America was always a very, very beautiful and expensive-looking place, and it’s where Superman lived and where Batman had the Batcave. That classic America from George Reeves to Adam West, just looked like a very aspirational place that I wanted to go. So I wanted to set a story there, but like ‘Mad Men’ has done, just a look behind that beautiful facade and actually just tell stories about real life.”

“Jupiter’s Circle” will peel back layers on the private lives of superheroes.

“It’s kind of like the episode of ‘Super Friends’ that was banned. It’s the idea of what happens between the episodes of ‘Super Friends,’ ” Millar said. “You’ve got their real private lives going on. A gay superhero is nothing new — we’ve seen that a million times in the last 10 years. But I thought: Wouldn’t it be interesting to be a gay superhero in 1958?”

When Millar returns to the present day in his “Jupiter” series, he’ll have a third generation in play, with a grandchild. Millar has always had a fondness for young heroes, but he said he wasn’t interested in creating a youthful hero who was trying to be cool.

“Whenever you get a youth character, he’s always got a haircut that’s about six months out of date, because the guy drawing the book is 45 [Millar’s current age], so the haircut is just slightly wrong, and they’re talking about breakdancing when everyone else is talking about ravers,” Millar said. “I liked the idea of doing a young character that wasn’t chasing youth culture. That what he was was just young and idealistic and loved being a superhero.”

In creating the “Jupiter” series’s youngest hero, Millar enjoys playing with the idea of being the third generation in a superhero line. Is the cycle of entitlement broken?

“Sometimes the grandchildren turn out just fine,” Millar said. “Quite often, children have more in common with the grandparents.”