Two's company, but three's a crowd -- at least in the realm of country vocal duos, and especially when the five duos competing for Vocal Duo of the Year at the 2015 ACM Awards are perfect just the way they are. While Florida Georgia Line are the most well-known of the bunch, the four other acts are gaining their own massive followings and are ready to battle it out for the prize.

The Brothers Osborne, comprised of John and T.J. Osborne, released their self-titled EP in September, with a full-length record expected in 2015. The siblings have a unique ability in their songwriting to understand the other's intentions fully.

"When we write, we don’t have to speak,” John Osborne admits. “We know exactly what we want, and we’re very honest. We used to fight when we were little kids, and we carried that to verbal attacks when we’re co-writing."

After the EP’s release, the band joined Eric Church on his The Outsiders World Tour -- quite the feat for new faces on the country scene.

Dan + Shay are quickly becoming a much-talked-about duo in country music. After their first single "19 You + Me" was released, they made their debut on the Grand Ole Opry stage, dropped their record, Where It All Began (with all tracks written or co-written by the duo), and extended their Where It All Began Tour into 2015. The duo's most recent single, "Nothin' Like You," recently hit radio, and they were also nominated for Vocal Duo of the Year at the 2014 CMA Awards.

Tyler Hubbard and Brian Kelley of FGL are the reigning winners in this ACM category -- one that Brooks & Dunn dominated countless times -- and they're also the CMA's Vocal Duo of the Year. The high-energy guys are also nominated for five more ACM Awards, including the night's highest honor, Entertainer of the Year. FGL released their sophomore (and gold-certified) record, Anything Goes, last fall, following up their massive Here's to the Good Times. They recently earned their sixth No. 1 with "Sun Daze."

The lone females of the category, Maddie & Tae are in it to win it. Madison Marlow and Taylor Dye met at the age of 15 and soon began singing together. If you don't know their names, you'll certainly know their hit song, "Girl in a Country Song," which became the first debut single by a female duo to reach No. 1 since the Wreckers did it in 2006, and the second in history.

"We couldn’t have guessed it would be like this,” Dye acknowledges. “Maddie and I were two girls with a big dream and a lot of determination. We wrote a song out of something a lot of people were talking about, and suddenly, people were talking about us. That’s when things got crazy.”

Their second single dropped in January, and their debut record is expected in June of 2015. They'll also serve as openers on Dierks Bentley‘s 2015 Sounds of Summer Tour.

Since the Swon Brothers' stint on The Voice, brothers Zach and Colton Swon have enjoyed more success.

"We’ve always had a fan base there, in our home state, but now we’re going places that I’ve never been to before, and people are buying every ticket,” Zach tells The Boot. “It’s insane. It’s the best feeling in the world.”

They were nominated for the 2014 CMA Awards' Vocal Duo of the Year and released their debut record in October, with major help and guidance from former The Voice coach Blake Shelton.

Who do you think will go home with Vocal Duo of the Year at the 2015 ACM Awards? Vote as often as once an hour in the poll below until the end of the day on April 15. We’ll tabulate the results and use them for our 2015 ACM Awards winners predictions the week before the show.

The 2015 ACM Awards will air live from AT&T Stadium in Arlington, Texas, on April 19 at 8PM ET on CBS.