As the youngest daughter of record producer Bruce Sudano and Boston-born disco icon Donna Summer, Amanda Sudano grew up around music, absorbing the sounds of Otis Redding, Sam Cooke and Joni Mitchell, as well as her mother.

“My mom would go out to the store, and people would recognize her, but it wasn’t like a big deal, like ‘Let’s keep it moving and get the Cheerios,’ ” Sudano says. While she and her sisters saw their parents’ passion for music, “we didn’t see the business or fame side,” she says. “It was more about doing what you love.”

Sudano shared that love for music from an early age, writing songs in preschool that she recorded in her dad’s studio, and her mom nurtured her singing. “She just told me to keep doing it, ’cause as a kid, I was super, super shy,” says Sudano, 33. “She’d hear me singing around the house and in my room, and if anyone told me to sing in public, I’d run the other way. She encouraged me to not be afraid.”

Now Sudano runs her own family-rooted act, Johnnyswim, with singer/guitarist and husband Abner Ramirez. Together, they spin a burnished, emotive blend of folk, pop, blues and soul that hit a peak in 2014 with the release of their debut album Diamonds, followed by A Johnnyswim Christmas. They’ll support that EP for a second holiday season when they play Royale with their band on Dec. 12 (ahead of a live album and Palladia cable special recorded for early 2016).

“It’s definitely our favorite time of year in a genuine way,” Ramirez says in a joint call from his mother’s home in Jacksonville, Fla., the day before Thanksgiving. He says they plan an even split of Christmas songs and originals on tour. “But we edit out some of our sadder Johnnyswim songs. We try to keep it up for the holidays!”

A Johnnyswim Christmas features the LA-based duo’s surging tradeoffs in “Have Yourself a Merry Little Christmas,” a choral-styled “O Come All Ye Faithful” and a sultry “What Are You Doing New Year’s Eve?” It’s more tempered than the urgent Diamonds, which reflected the loss of both Sudano’s mother (Summer died from cancer in 2012) and Ramirez’s father and begins with the title track’s opening salvo, “In the wake of every heartache, in the depth of every fear, there were diamonds, diamonds waiting to break out of here.”

“We do our best to honor that emotion, that sense, that feeling, in whatever we write or create, even when we cover a Christmas song,” says Ramirez, 32, who grew up listening to Cuban music, especially passionate love songs or boleros.

In contrast to Sudano, Ramirez envisioned a musical career. “For sure, at 6 years old, realizing you could have a job singing songs, that was the only plan,” he says. Sudano counters, “My biggest issue was if I was good enough to actually make a living doing it.” She successfully pursued modeling on the side in New York.

They first met at church in Nashville, where Sudano’s family had moved during her teens, although they didn’t really connect until four years later, when she and Ramirez met at a coffee shop in 2005 and he invited her to one of his shows. “I knew he was super-charming and wonderful, but I had no idea he did anything musical,” Sudano says. “As soon as I found that out, I was like, ‘Oh, snap, it’s about to go down.’ ”

Ramirez had already taken an interest, noting he was “cyber-stalking” her for some time. “I said I was not trying to really pursue [music] anymore because I got burned,” Ramirez recalls of their conversation, referring to a failed record deal. “And she said, ‘That’s stupid. We should write.’ And I thought, ‘Absolutely we should write…’ It was purely an excuse to be alone together.”

They soon formed Johnnyswim, married in 2009 and now have a 9-month-old son who joins them on tour. “One of the greatest strengths of a marriage is to have adventure,” Ramirez says, “and we certainly have more than our fair share of adventure.”

Johnnyswim plays Royale on Dec. 12.