The alt-rock mainstays showed off their pop muscle -- and started playing to the biggest audiences of their careers -- with the release of 2013's Heartthrob; Tegan and Sara Quin are currently working on the follow-up to that much-lauded full-length.
Best known for their U.S. crossover hit "All The Things She Said" and its music video's controversial faux-lesbianism, the Russian pop duo of Julia Volkova and Lena Katina continued putting out albums following their 2002 breakthrough, but officially disbanded for the final time in 2014.
With their run of hits between the mid-80s to early 90s, Naomi and her daughter Wynonna became one of the most successful country duos of all time, and continuously collected Grammys in the best country performance by a duo or group with vocal category. After Wynonna developed her musical skills while playing alongside her mother in Kentucky, the Judds found considerable success with tracks like "Cry Myself to Sleep," "Have Mercy" and "Grandpa (Tell Me 'Bout The Good Old Days)."
Before their recent comeback bid with their self-titled album, the Australian twin-sister duo enjoyed minor U.S. popularity -- but developed a cultish fan base -- thanks to hits like "4ever," "Untouched" and "Everything I'm Not."
Once known as Aly & AJ, the sister duo of Aly and Amanda Michalka remade themselves from Disney Channel stars into affable pop-rock personalities, and released three albums before changing their name to 78Violet. An under-appreciated new single, "Hothouse," was issued in 2013.
You know a Shampoo single even if you don't realize it: Jacqui Blake and Carrie Askew's pop-punk project scored a smash with "Trouble," the lead track from their 1994 debut We Are Shampoo with an unforgettable hook ("Uh oh, we're in trouble…"). Sadly, Shampoo only existed for one more album, 1995's Girl Power.
Mel & Kim
Sisters Mel and Kim Appleby boast one still-undeniable dance hit, 1987's "Respectable," as well as a effervescent debut album, F.LM.; tragically, Mel was diagnosed with cancer soon after the duo hit it big, and died at the age of 23 in 1990. Kim later continued as a solo artist, but never achieved the same dizzying heights as the pair scored in the late 80s.
After spending nearly a decade with Bananarama, Siobhan Fahey formed Shakespear's Sister -- originally conceived as a solo project, but eventually becoming an official duo with singer-songwriter Marcella Detroit. The group's second album, 1992's Hormonally Yours, was the home of Shakespear's Sister's biggest hit, the rapturous "Stay."
Maddie & Tae
After meeting in 2014, Maddie Marlow and Tae Dye decided to team up and scored an unexpected country smash with "Girl in a Country Song." A follow-up single, "Fly," was recently released to preview the pair's upcoming debut album, Start Here.
A spectacularly named U.K. dance group, Booty Luv cracked the pop charts across the pond with the debut single "Boogie 2nite," which would also serve as the title of their 2007 debut album. Cherise Roberts and Nadia Shepherd formed the duo after previously serving as members in the R&B group Big Brovaz.