John Legend Says Gwen Stefani Is Blake Shelton's 'Weakness' on The Voice: 'She Softens Him!'

Brianne Tracy

When it comes to coaching The Voice, Blake Shelton and Gwen Stefani seem to be each other’s kryptonite.

Ahead of the hit NBC singing competition series’ premiere on Monday night, the couple and their fellow coaches, John Legend and Kelly Clarkson, caught up with PEOPLE about what it’s been like working together on season 17 so far — and it appears Shelton and Stefani’s romance has made for an interesting dynamic.

“I never really spent time with Gwen before, but it’s been so much fun getting to know her and see her and Blake together,” Legend, 40, told PEOPLE. “It’s a different side of Blake, seeing him with Gwen. I feel like she makes him better and she softens him up a little bit. She’s his weakness.”

In response to Legend, Stefani, 49, said about Shelton, 43, “He’s my weakness, I’ll tell you that right now.”

John Legend and Gwen Stefani | People Now

According to Shelton, though, Stefani is “taking 100 percent advantage” of the situation. For example, Clarkson, 37, notes Stefani has said, “Blakey, I want this one,” on the show when going head-to-head with him for an artist they both want on their teams.

“I’m going to fight for people that I think are great,” Stefani said. “If that means having to fight Blake hard, I’m gonna’ do it.”

RELATED: Gwen Stefani Says She Didn’t Know Boyfriend Blake Shelton ‘Existed’ Before The Voice

Clarkson said that Stefani and Shelton are like the “mom and dad” of the coaches’ panel.

“I love every time mom and dad argue,” she joked, before quickly clarifying, “They don’t argue. I’ve never seen y’all argue. I don’t even know if they do argue. They have this really cool relationship that’s fun to watch. It’s a really nice breath of fresh air.”

Blake Shelton and Gwen Stefani | Trae Patton/NBC/NBCU Photo Bank/Getty

Stefani — who has served as a Voice coach on-and-off since 2014 — was asked to return to the show after longtime coach Adam Levine announced his departure in May.

“To be honest it’s strange to not have him here,” Shelton said. “He’s never not been here, you know? And it’s just that guy that’s just over there constantly just makin’ you want to strangle him. And now he’s gone and it sucks, to be honest with you. But havin’ Gwen back, for me, makes it a lot more fun.”

RELATED VIDEO: Blake Shelton Misses Adam Levine on ‘The Voice’ but Gwen Stefani Helps Make It ‘Fun’

Shelton and Stefani first met on the set of the show in 2014. Seven months later, after both of their respective divorces (Shelton to fellow country star Miranda Lambert and Stefani to Bush lead singer Gavin Rossdale), the two struck up a romance and have been happily together ever since.

“Every season I’ve worked with Blake has been completely different because I’ve been in different places in my life,” says Stefani, who will celebrate her four-year anniversary with Shelton in November. “This time’s my favorite because we know each other so well.”

Gwen Stefani and Blake Shelton | Harmony Gerber/Getty

As to whether he and Stefani tend to take their work home with them, Shelton said, “It’s impossible to not.”

“We’re on The Voice together, so obviously, if something crazy happened, we’re still going to be talking about it when we get home,” he said. “And a lot of pillow talk about our artists and stuff.”

Season 17 of The Voice premieres Monday, Sept. 23 at 8 p.m. EST on NBC.