Brian could be seen singing along as his son took the stage to perform his original track “Hey Jesus”

You could see the shape of Brian Littrell’s heart as he watched his son Baylee Littrell perform.

During the Monday, March 31 episode of American Idol, the Backstreet Boys band member, 50, got emotional as his son, 22, paid tribute to his late grandmother with an original song.

Before singing an original track called “Hey Jesus,” Baylee explained why the song was so meaningful.

“I wrote this song when I was going through a pretty tough time in my life,” he began. “Lost somebody I’d loved. My grandma was my best friend.”

Baylee and Brian Littrell on American Idol.Disney/Eric McCandless
Backstreet Boys’ Brian Littrell Has an Emotional Reaction to His Son Baylee’s American Idol Audition

Added Baylee, tearing up: “With my dad being away on tour, she would always step in. She understood me like not many people do. My grandma passed away three years ago, almost.”

“I thought she was gonna be around for moments like this. I never expected to lose her, so when I did I questioned everything,” he said.

That included his faith, which Baylee thought he had lost permanently.

“This song kind of helped me find it,” the “Don’t Knock It” singer said.

Baylee then belted out the track while he played acoustic guitar.

Baylee Littrell; Brian Littrell.American Idol/Youtube

As he was singing on stage, the camera panned to his father who could be seen proudly mouthing the words along.

After Baylee finished his set, Carrie Underwood praised his performance.

“Baylee, you’re so good. You’re heart and your genuineness just coming through. You’re so good,” the country star, 42, told him.

Backstreet Boys’ Brian Littrell Is ‘Super Proud’ of Son Baylee, 22, for ‘Busting His Butt’ on Upcoming Season of Idol

Last night’s performance wasn’t the first time Brian got emotional while watching his son perform on American Idol.

When Baylee auditioned for the show last month singing an original song about wanting to give up, called “Waiting on Myself to Die,” the “I Want It That Way” hitmaker was visibly emotional throughout the entire audition.

Brian said he was “super proud” of his son, who had “obviously grown up in the business and he’s cut out for it.”

After Luke Bryan asked the father-son duo if they ever sang a song together, the pair harmonized.

Baylee was then offered a golden ticket straight to Hollywood, which prompted Brian to tear up.