He may have won an Oscar for his role in 2005’s Syriana, but the true tour de force performance of George Clooney‘s career is no doubt his latest. Just ask his wife, Amal Clooney, and their 10-month-old twins, Alexander and Ella.

“George acts up a storm when he reads Dr. Seuss books to his kids at bedtime, even though they don’t understand the words yet,” a friend of the doting dad tells Closer. “He does high voices, low voices — he really gets into all the characters. It makes the kids and Amal laugh each and every time!” And his son “laughs louder than anyone in the room,” George boasts. “It’s the funniest thing.”

These days, George spends as much time rolling around on the floor of his kids’ room as he does walking Hollywood red carpets — and he’d have it no other way. “What a great father he is,” Amal, 40, gushes of the man she married in 2014, three years before she turned America’s most eligible bachelor into a first-time dad at the age of 56. Now, as George turns 57 on May 6, he’s as amazed as anyone with how much his kids have transformed his life.

“It’s wild. The first thing you think is, I hope I don’t screw this up,” he says of the joys and challenges of fatherhood, which is why he recently pulled out of starring in Hulu’s Catch-22 series. “He knows he’s getting older,” the friend says, “and he needs to be sure he’s healthy for his twins. He wants to conserve his energy, and stepping back from that project is a part of that.”

George was devoted to his kids from the get-go, awaking every three hours with Amal while she was nursing. “If I don’t get up, I feel guilty,” he joked at the time, noting that while it was a lot of work, his life as a new dad was also lots of fun. “I’m a very good diaper guy,” he says with a grin. “You should see when my friends show up and see me change a diaper, the laughter that comes from them!”

Celebrity baby nurse Connie Simpson, author of The Nanny Connie Way, came out of retirement to make sure George was up to this particular challenge. “He embraced the situation,” she tells Closer. “He did a really good job and stepped up to the plate whenever it was time. I didn’t even have to ask!” While it’s hard for many to believe the actor doesn’t miss his wild bachelor days, he’s emphatic. “I sure don’t,” he insists, proudly adding, “Now my house is filled with the warm sounds of babies crying.” The most precious moments with Amal, Alexander, and Ella start early. “Between six and eight in the morning we get to have them in our bed,” says Amal, a renowned English barrister specializing in international human rights law, adding that phone calls are never scheduled before eight. The rest of the day depends a lot on where they are.

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George and his wife, Amal.

“Their lives are always changing,” says the friend of the jet-setting couple, who are spending the spring in NYC while Amal’s teaching at Columbia University and working for the United Nations. They also have homes in LA, on a tiny island in the Thames in England, and in Lake Como, Italy, the latter being an 18th-century villa George bought for about $10 million in 2001. “They meet high-level people all the time,” says the pal. “They’ll hang out with their friends and watch old movies one night, then the next they’re dining with Barack Obama and Michelle Obama. They have big lives, and they just try to roll with it.”

While the couple does have full-time nanny help, the friend adds, “George and Amal are as hands-on as they can be. Their rotating three nannies will blend into the background so they can be alone with the kids.” That family time is cherished. “They feel they are the two luckiest people on the planet to have found one another. They’re in bliss, and they’re happiest when they are home.”

That’s when George gets to really let loose and have fun with his “knuckleheads,” his playful nickname for the twins. “He plays with them all the time with their building blocks and toys. And he loves to read to them,” the friend says, explaining that in addition to Dr. Seuss stories, George is partial to Clifford the Big Red Dog and James and the Giant Peach. “He’s so thrilled with it all that if the kids throw up on him, he doesn’t even get embarrassed. He just laughs it off.”

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After dinner, it’s more playtime, then baths, stories, and bed. “It’s all very normal,” the source says. Ever the romantic, George made sure Amal got the sweeter end of one of the twins’ bigger milestones. “We’ve had some ‘Mamas’ and ‘Dadas,'” she reports, “[but] George was very careful to ensure that ‘Mama’ was their first word.” Even better? “I’m the cook in the family,” George boasts, and he’s also very generous in giving his wife spontaneous shoulder massages.

Being such a devoted husband and father, though, has cut into his hang-out time with his buddies, like Brad Pitt, Julia Roberts, and Rande Gerber, and his wife, Cindy Crawford. “When they’re in LA, George’s loyal entourage will come over for movies and basketball games, but those times are fewer and fewer,” the friend shares.

George and Rande sold their Casamigos Tequila company last year, with George’s share coming in at a reported $200 million. He also has an estimated $100 million Nespresso endorsement deal, which makes it easier for him to focus on his family over movie roles at this stage of his career. (George is generous with his fortune; in 2013 he reportedly gave $14 million to a group of close friends.)

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Amal, George, Rande, and Cindy.

It’s been two years since he’s acted in a film, “and I am not really sure when the next version of that will be,” he says. Besides, he adds self-deprecatingly, “I’m not a leading man anymore. Nobody wants to see me kiss the girl.” His fans — and Amal — would disagree, but George is content to stay behind the camera for now, poring over scripts as he looks for a project he might want to direct. More important is ensuring his children get as fulfilling a childhood as he had. “He wants his parents to be involved with Alexander and Ella as much as they can,” the friend says of journalist Nick Clooney, 84, and his wife, Nina Bruce Warren, 79.

Amal even put two swinging benches on the back porch of their British home as a nod to George’s youth. “I tried to incorporate something of Kentucky,” she says of where George was born and largely raised. His small-town roots also helped nurture the fun-loving guy that everyone adores. “He liked to prank around a lot, and he played softball, baseball, basketball,” Ronnie French, one of George’s friends from Augusta, KY, tells Closer. “He’ll just love his kids and they’ll have a great time with him, too. He’s still a big kid himself!”

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George as a kid.

That big kid is a responsible one: George has been asking friends John Krasinski and Emily Blunt (who are also raising their kids in both the US and Britain) how best to work out all the intricacies of the twins’ schooling and residence. Looking after Alexander and Ella’s well-being, after all, is the greatest role George has ever had. “I want them to have a sense of humor. I want them to be interested in things,” he says of his dreams for his twins. “I want them to be happy.”

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