EXCLUSIVE: Thomas Rhett Talks Bringing His Kids Onstage and Teaching Willa Gray to Be a Fashionista

"I'm ruining her already!" Thomas Rhett admits with a laugh. 

The 27-year-old country crossover star is talking about his 22-month-old daughter, Willa Gray, who is already showing signs of being a fashionista in the making. 

"Every time she wakes up, the first thing she says is, 'Closet, shoes' and she goes in there and picks out what she wants to wear for the day. It's pretty hilarious," Rhett tells ET. "I am in trouble, I know. It's bad."

Since adopting Willa Gray from Uganda earlier this year, Rhett has been sharing his own love of fashion -- specifically, sneakers -- with her. Meanwhile, he's partnered with Daniel Patrick, Madeworn, New Era and his personal stylist, Kemal Harris, on a collection of limited edition, high-end merchandise, proving it's not all about cowboy boots and belt buckles in the world of country music. 

"Every time I go onstage, I'm trying to wear something different. Especially with my merch, I'm just trying to make it -- I don't know, just expand a little bit," he told ET at his a recent pop-up shop in Los Angeles. "It's something I've been pretty passionate about for a while now." 

Wearing a black T-shirt, jeans and yellow sneakers, Rhett completed his street-style look that day with a gold necklace -- a gift from his wife, Lauren -- engraved with each of their daughters' names. The couple welcomed baby Ada James in August. 

"My life has changed so much over the last couple of years and especially this year," Rhett said. "Having two little girls under two has been life-altering, but it's been super fun and we're so blessed with two beautiful little girls." 

The couple's pregnancy was a surprise, and it came amid the year-long process of adopting their first child. Rhett sings about the experience on the title track of his third studio album, Life Changes, which became the first country album to debut at No. 1 on the all-genre Billboard 200 chart this year. 

"I was really surprised," he admitted of the milestone. "I think as an artist, any time you put a record out you're just like, 'God, I hope people like it.' So when you see your record go number one and stay there for an entire week, that was, like, a huge feat." 

Rhett said that his girls "each have their favorites" when it comes to album cuts. Wife Lauren loves the song "Sweetheart," while Willa Gray gravitates towards the EDM-flavored "Leave Right Now." 

While Rhett has been working hard to balance his increasingly hectic home life with his Home Team tour, he's relished the moments when the two collide. Willa Gray hilariously "went rogue" during a recent show in Pennsylvania, as documented on Lauren's Instagram account. 

"Dude, that girl. She's crazy," Rhett joked. "She, like, hopped out of Lauren's arms and just started sprinting backstage and Lauren had to go chase her down." 

That same night, Lauren, Willa Gray and Ada James briefly joined the proud papa onstage, resulting in an adorable family moment. 

"My wife hates coming onstage, but literally, I'm sitting there playing a song and all the people in the front row were looking side stage, they're not even watching the show," he recalled. "They're sitting there waving at my wife and I was like, 'Babe, you got to come out here.'"

The girls also flew out to Los Angeles to surprise Rhett ahead of his performance at The Greek, with Lauren and Ada James making a quick appearance during his set. Another surprise: dad Rhett Akins taking the stage to perform together on their song, "Drink a Little Beer." 

"I'm tireder than I've ever been, but I think I've gotten used to it," Rhett said of his new life. "I think before my kids, my biggest fear was like, 'How am I gonna function with no sleep?' But I think it's become a new norm and days are a lot different, but they're packed full of surprises, that's for sure." 

You can see the full interview and more from Rhett's fashion collaborations on this week's episode of Certified Country, below.