Sister Act: Alana (19), Este (24) and Danielle (22) comprise the band Haim.
I first became aware of the band Haim after seeing Danielle Haim play backup for Jenny Lewis on her 2009 tour. She really stood out as a skillful musician, contributing vocals, guitar, drums, tambourine. I met her after the show just to give her props, and after doing some research, found that she had also played for the Strokes' Julian Casablancas and was in a band with her two sisters, Este and Alana. They were heavily influenced by their musician parents growing up in Southern California, and even played in a folk band with them as kids.
The trio recently released their debut EP Forever, which you can download it for free here -- I highly recommend it. They grew up listening to such bands as the Fleetwood Mac, the Beatles, the Doors and the Eagles, and it's apparent in their sound -- but they also manage to blend in some R&B influences. Said guitarist Alana in an interview with Vogue,"I think we still have the structure of old-school rock. But the R&B adds the spice."
This particular 2009 live performance of a song called "The Wire" turned me into an immediate fan.