A second generation of Nelsons and Jennings carries on a family tradition with a new duet on an old song. Lukas Nelson and Shooter Jennings have teamed up for a cover of the country classic "Mammas Don't Let Your Babies Grow Up to Be Cowboys," originally sung by their fathers -- Willie and Waylon, respectively, of course -- in 1978.

Written by Ed Bruce, the younger Nelson and Jennings' version of "Mammas Don't Let Your Babies Grow Up to Be Cowboys" has served as the theme song for the Netflix series The Ranch since its premiere in 2016. However, with the show -- which stars Ashton Kutcher and Elisha Cuthbert, among others -- set to end in 2020, the pair have released the full song.

“Lukas and I had a great time in the studio. We came up with an alternate rhythm that changes the vibe a little bit from the original — that gave us the space to make it our own,” Shooter Jennings tells Rolling Stone. “He and I have had very close relationships with our fathers — they always were our number one fans. I’m so happy to have had the opportunity to sing this song with my brother and just have fun with it.”

Adds Lukas Nelson, “Working with Shooter was an honor. We had a great time in the studio and I would love to do it again many times." The pair have toured together before as well.

Shooter Jennings and Lukas Nelson's new version of "Mamas Don't Let Your Babies Grow Up to Be Cowboys" will appear on a new The Ranch soundtrack, out Friday (Jan. 24). The project also features music from Lee Brice, Wynonna Judd and more.

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