Their song is the slamming screen doors Philadelphia's newest carol.

Travis Kelce is following in Grammy winning girlfriend Taylor Swift's musical footsteps. Indeed, the Kansas City Chiefs player joined his big brother Jason Kelce on the Philadelphia Eagles player's Christmas album with The Philly Specials. Travis was a special feature for the "Fairytale of Philadelphia," a playful twist on The Pogue's 1987 song "Fairytale of New York."

In the Irish folk-inspired recording, the two NFL superstars exchange barbs with one another. 

In one verse, Jason, 36, sings, "You smell like some old scum / washed up from the Schuylkill," to which Travis, 34, quips back, "You dirtbag, you phony / Happy Christmas you ass / I pray God it's our last."

But amid the many jabs and references to the City of Brotherly Love, the duo's own brotherly love does indeed shine through. 

In response to Jason's sung accusation, "You took my dreams from me / When mom first had you," the tight end sings, " I kept them with me, Jas / I put them with my own / Can't make it all alone." 

The brotherly duet is one of the three songs the Eagles musical group—which also features players Jordan Mailata and Lane Johnson—has released so far this year, with the others including Mariah Carey's iconic "All I Want for Christmas" and "This Christmas," featuring the song's original artist, Patti LaBelle. The proceeds from the album support the Children's Crisis Treatment Center, a non-profit that "specializes in delivering behavioral health services to Philadelphia's children and their families."

Travis' singing debut comes shortly after he traveled to Argentina to support his girlfriend as her Eras Tour embarked on its South American leg. And after attending her show—in addition to reacting to Taylor's shoutout in "Karma"—the athlete had nothing but rave reviews for her performance. 

"I was enjoying myself down there in Buenos Aires," Travis said during the Nov. 15 episode of his and Jason's New Heights podcast. "The show was even more electric knowing that I had a little bit more to enjoy for, and yeah, Taylor absolutely ripped it. She killed it, and it looked like she was having some fun up there."

His attendance at the concert, made possible thanks to a bye week for the Chiefs, comes after Taylor herself has shown up to a number of Travis' NFL games. 

To relive some of Taylor's best football moments—and her stellar Game Day outfits—keep reading. 

While supporting Travis Kelce as the Kansas City Chiefs faced off against the Chicago Bears on Sept. 24, her first-ever NFL game at Arrowhead Stadium, Taylor Swift sported DÔEN's white Lois Tank and Ksubi's distressed denim shorts, which she paired with a Chiefs windbreaker and matching New Balance sneakers.

For the Chiefs' Oct. 1 game against the New York Jets, held at MetLife Stadium in New Jersey, Taylor wore Area's denim shorts, which quickly sold out. The singer completed the look with Christian Louboutin boots and Gant's relaxed leather shirt.

And Taylor couldn't forget her signature red lip for the star-studded game.

For the Chiefs' Oct. 12 game, where she spent time with Travis' dad Ed Kelce, Taylor wore a Chiefs jacket from WEAR, a line by Erin Andrews (who Travis has credited for connecting him with Taylor).

Taylor, who also spent time with quarterback Patrick Mahomes' wife Brittany Mahomes at the game, sported a Balenciaga corset top underneath the Chiefs jacket.

Taylor had an extra special accessory on her wrist for the Chiefs' Oct. 22 game: An Erimish bracelet with Travis' jersey number on it.

...we can't calm down.