On Sunday evening, Kieran Culkin is up for the best supporting actor award at the Baftas. If he wins, he will probably give one of his startled, free-wheeling and characteristically funny speeches, though by now he may struggle to express surprise, given his extended run of triumphs at these events.

In 2024, he picked up a Golden Globe for best actor in a television drama series for his performance as Roman Roy in Jesse Armstrong’s Succession. Last month, he nabbed the Golden Globe for best supporting actor for his role as Benji Kaplan in Jesse Eisenberg’s A Real Pain (he seems to respond well to direction from men called Jesse), which also landed him the four major American film critics awards, made him an odds-on favourite for an Oscar next month, and accounts for his Bafta nomination.

All this attention may seem rather sudden, as though he were an overnight sensation, but Culkin, who appeared in Home Alone alongside his then famous older brother Macaulay, has been in the acting business for over 35 years. He is still only 42.

If he has spent most of the intervening four decades flying under the radar, it may have something to do with witnessing close up the effects of premature stardom. His brother was one of the biggest box office stars of the early 1990s but was in danger of burnout by the time he was 14. “I don’t personally know anybody that has hit a level of fame that likes it,” he said recently. “I did have a somewhat unique perspective of having been around it in my childhood, watching that being like, ‘Oh, I get it. That sucks’.”

Suck it may, but fame also has a tendency to suck in all but the most determinedly resistant once the acclaim and money start rolling in. When he was 19, Culkin was nominated for a Golden Globe for his performance as a prep school dropout in Igby Goes Down. It drew offers for bigger films but he rejected them. “I was definitely not ready,” he has admitted. “I would not have been able to handle it.”

He’s still wary of accepting major parts, although now his concern is more to do with being taken away from his wife, Jazz Charton, a Londoner, and their two young children. His rule is no more than eight days of separation. For that reason, he nearly pulled out of A Real Pain, which involved filming in Poland.

While there’s little risk of Culkin snatching lead roles from Leonardo DiCaprio, he has made it very difficult for casting agents to look anywhere else when it comes to idiosyncratic characters with an unfiltered way with words.

In A Real Pain, a deftly observed comic drama following two awkwardly matched cousins on a Holocaust tour in Poland, Eisenberg (playing one of the cousins) gives a moving speech to his fellow tourists about what it’s like being closely related to Benji (Culkin). He loves and hates him, he explains, and is often infuriated by his unpredictable ways, but he’d give anything to experience what it’s like to light up a room the way Benji can with his unbounded personality.

It’s a film that, for all Eisenberg’s sharp script and thoughtful direction, is close to unimaginable without Culkin’s unique charm – as engaging as it is unsettling. Yet with it, it all seems so utterly natural that it couldn’t not be made.

That it was made is, in its own way, a minor miracle. It’s not just that Culkin came close to withdrawing several times, and Eisenberg was uncertain of his participation until he turned up on set, but also that he isn’t Jewish. Taking into account the story’s emotional underpinnings, and the debates surrounding ethnicity and casting, Culkin could have been a controversial choice. He immediately raised the issue with Eisenberg, who told him that it didn’t matter. One measure of his success is that Eisenberg was right –it doesn’t.

A potentially more challenging hurdle was that the writer-director had never seen Succession and didn’t even ask Culkin to audition. When Armstrong heard this, he was so confounded that he thought Eisenberg must be lying. In fact, it was the director’s sister who advised him to hire Culkin after she read 30 pages of the script.

She had watched Succession. And, once seen, Culkin’s Roman can’t easily be forgotten. How do you play a potty-mouthed billionaire nepo-brat with delusions of competence, a father-fixation, a contorted parasexual obsession with a much older colleague and a comic knack for exposing others and humiliating himself? Again the only conceivable answer is exactly like Culkin did it. Or rather, how he learned to do it.

His absurdist sensibility was always there, perhaps shaped by a childhood of which he speaks fondly but which was, by conventional standards, decidedly weird. The fourth of seven children, he began auditioning for acting parts when he was six. He not only glimpsed the warping effects of Hollywood at an early age but also hung out at Michael Jackson’s Neverland ranch, taking helicopter rides with the singer, who, he says, was only ever warm and friendly.

His father, Christopher “Kit” Culkin, was a former New York stage actor who, Macaulay alleged, “was physically and mentally abusive”. He walked out when Culkin was 12, and there followed a bitter custody dispute. The children remained with their mother, and father and son have not spoken for over a decade.

An older half-sister died of a drug overdose when he was a teenager, and another sister, to whom he was very close, died in car accident when he was in his mid-20s. He remains devoted to his mother, Patricia Brentrup, herself one of 11 children. Culkin never completed high school.

Yet if all that frenzy and dislocation informed his restless-sarcastic schtick, it was his five-year stint on Succession that really developed his spontaneity. At first, he was reluctant to improvise, which was the way the showrunner Armstrong sometimes liked to work. But once he came round to it, he made impulsiveness his own thing, arguably his defining talent.

At the end of the first season, Culkin, who’d then been acting for 30 years, came home and said to himself: “This is what I want to do with my life. I think I want to be an actor.”

The unrehearsed creativity that Armstrong helped unleash at first confused and alarmed Eisenberg, a natural worrier who plans every detail in advance. By contrast, Culkin prefers to arrive on set not knowing what scene he’ll be doing so that he can stay fresh and in the moment. Although he learned his lines, he refused to say them out loud until they were shooting.

The two approaches seemed as antagonistic and fraught as their characters in the film. Eisenberg called his co-star “mercurial, unknowable, unpredictable”.

Yet they managed to find a compromise that, like the ill-paired cousins they played, worked a dream. The director would call Culkin’s “the greatest performance I’d ever seen”. That may be the hyperbole of man who’s keen to sell his film, but it is a remarkable performance, as close to charismatic chaos and disinhibited truth-telling as anyone viewing it would want to get.

Of course, it’s only acting, a fact that sometimes gets lost amid the celebrity industrial complex of film promotion. Luckily, one of the people most likely to keep that reality in mind is the man who is the focus of all the praise. He says he doesn’t care if a film he is in flops – he has done his job and it’s not his responsibility. That only makes sense if it works the other way too, and he doesn’t care if it’s a hit either.

All things considered, Culkin may just be that most rare of creatures: an actor who doesn’t take himself – or anything else – too seriously.