It's the battle of the teens on "The Voice."
Kelly Clarkson strategically paired 13-year-old Hailey Mia against The Cunningham Sisters, a duo composed of 14-year-old Marie and 15-year-old Macie, during the second round of Knockouts Tuesday.
"I wanted them to feel challenged by each other because they’re the same age," Clarkson said, before realizing her plan also means she has to send one of them home. "It’s going to be really hard to choose."
Mia selected Duncan Laurence's "Arcade" to showcase her "old soul." The Cunningham Sisters tapped into their gospel roots on Hillsong UNITED's "Oceans (Where Feet May Fail)" because they "came together as a duo on worship songs."
The tiny powerhouses didn't crack under pressure and sang like true veterans.
John Legend called them "babies" and Blake Shelton said their performances were the "cutest thing I've ever seen." Clarkson literally hid behind her own hair.
"As a mama, this is so hard," Clarkson said. "You’re all so gifted and so young, so you feel like such a jerk being, 'Sorry, I picked the other one.' "
Clarkson eventually picked Mia because she "came alive" during her rendition. Legend and Shelton, the only coaches with a steal in play, didn't use it on the duo.
Legend did use his steal, however, to swoop up Team Ariana Grande's David Vogel, who sang an acoustic version of Selena Gomez' "Lose You To Love Me" with only his guitar.
Legend said his 5-year-old daughter with Chrissy Teigen, Luna, would approve of Vogel's version: "My daughter is a big Selena Gomez fan and I liked how cool and different your version was."
Vogel's performance of Gomez's hit song also included an epic hair flip, which caught Shelton's eye. "I've never had the confidence to fix my hair while playing guitar at the same time," he said.
Clarkson quipped, "You had a mullet for a while so it was all in the back."
Although Vogel was booted from Team Grande after losing to Ryleigh Plank following her "free spirit" rendition of Miley Cyrus' "Midnight Sky," he promised to get a tattoo in honor of Grande. But his new coach wasn't so sure about that.
"I don’t know about this tattoo now," Legend said.
Knockouts continue on "The Voice" next week 8 EDT/PDT on NBC.