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At first, Brad Paisley wasn't sure what was going on. One ordinary day last year, the country singer spotted his toddler son William Huckleberry—Huck for short—waddling toward him while waving a white stick. Trailing behind Huck was Brad's wife, actress Kimberly Williams-Paisley, capturing their son's crusade on video. And then the country singer noticed that the white stick was really ... a home pregnancy test. "I knew something was up!" he says, laughing. "I figured Kim was either leaving me and doing it in a cruel way—or it was good news."

Actually, it was great news: Huck, now 2, was going to be a big brother. "We thought our kids could be close in age and play together," says Kim, 38, who welcomed the couple's second son, Jasper Warren, on April 17. But with two babies in diapers ("We haven't potty-trained Huck," she says), "it's challenging. Two feels like more than two. It feels like five sometimes! But we're so fortunate that Jasper is happy most of the time." It helps too that Huck is eager to bond with his new playmate. "He'll take a book to him and point out a bulldozer, and Jasper just bobs his head and smiles," says Brad, 36. "It's funny to watch."

There's plenty to smile about at the Paisleys' Franklin, Tenn., farm, which stretches over 85 acres. In the family's 6,500-sq.-ft. log-cabin home, the kitchen is stocked with soy and gluten-free food for the boys ("I'm one of those annoying moms giving their kids replacements for what normal kids would eat—but I'm not militant about it," says Kim, who serves up pancakes and bacon on Sunday mornings) and the kids' bedtime hovers around 9 p.m. "Brad is a man who works at night," Kim explains, "so our family is on a later schedule." There's also a barn, a pond where Dad can teach his sons all about his favorite pastime, fishing, and a building that houses Brad's excavation equipment, an interest Huck inherited from his old man. "Huck's obsessed with bulldozers," says Kim, adding that the toddler owns mini-versions of his daddy's digging machines. "There are little-boy toys and big-boy toys everywhere!"

When the couple found out the newest pint-size Paisley would be another bulldozing boy, "We were thrilled," says Kim. "Huck was a surprise. For the second one, I wanted to plan." But while Kim admits, "I read every pregnancy book I could get my hands on" for her first child, during her second pregnancy, "I winged it a little more and trusted my instincts. I was more easygoing with Jasper, and he's more easygoing too." So much so that Jasper made his entrance into the world two weeks past Kim's original due date.

Huck was a different story. "Huck was three days early," recalls Kim. "Which is appropriate," adds Brad. "He's not a laid-back kid. He's a go-getter. He's ready to go when he gets up." A "very animated, fiery and dramatic" child, according to his mom, Huck happily sings the ABCs for guests and proudly shows off his daddy's guitars—and even plucks a few notes on the banjo—located in a room of the 100-year-old farmhouse on the property where Brad wrote his latest album, American Saturday Night. And while Huck can name every member of Brad's band, the curious kid is still puzzled over what everyone else in the world does. "The greatest question he's asked is, 'Mommy, does Jesus play the banjo?'" says Brad.

Despite the addition of a new little fella to the family, the couple, who wed in 2003, learned to maintain harmony in their household by taking child care in shifts. Kim wakes up for Jasper's night feedings, and Brad rolls out of bed early to make the morning coffee. "That's supportive!" says Kim. Brad also helps tuck in Huck for his afternoon nap, which usually involves reading his favorite books. ("He's got Where the Wild Things Are about memorized," says Brad.) While the Paisleys don't have a nanny, they do rely on a regular babysitter and on Brad's parents (a.k.a. Gramzy and Grand-dad), who live about 10 miles away, for extra help. "They give us date nights, which is important," says Kim, who is taking a break from acting and instead working on a young-adult novel with her dad, a retired freelance writer. "I don't want to be anywhere else but with the kids right now."

Nor is she ready to entertain the idea of expanding the brood yet again. "We're not thinking about that right now," says Kim. "I've got two hands, two arms—and two boys." She then glances at her husband sitting on the couch next to her and, with a smile, corrects herself: "Three boys!"

FOR MORE ABOUT BRAD, GO TO PEOPLE.COM/BRAD_PAISLEY