Have you heard of them?

The Cimorelli sisters! They're a female singing group composed of 6 girls which are all related to each other. The oldest is Kristina who's 20 years old, then Catherine who's 19 years old, Lisa who's 17 years old, Amy who's 16 years old, Lauren who's 12 years old and Dani who's 11 years old. As you can see, in this video in which they did a cover of "Best Love Song" by T-pain and Chris Brown, their names are mentioned according to their age from oldest to youngest, so you'll get to see who's who. They've got other covers in youtube. I wasn't sure how they became youtube famous.. but I guess i started out when they posted their videos in youtube or maybe when they had concerts in places. If you hear their voices, you'll really be amazed! And they're all good-looking too! :D
THEY'RE JUST AWESOME! ;)

Here's a video of their cover with auto tune..

Here's another video of their cover without auto tune..

"The Best Thing I Ever Had" by Beyonce