Pop stars-turned-designers Jessica Simpson and Ashlee Simpson are teaming up for a new clothing line. The singing sisters are to collaborate on a line of tween apparel featuring sportswear, denim and activewear in their first fashion venture together, which will be part of the Jessica Simpson Collection.

"Creating a tween apparel collection was a natural extension for the brand. I'm excited to bring my sister, Ashlee, along as co-creative director of this division, because she brings a savvy rocker edge that defines today's tweens," said Jessica, whose fashion empire is set to be worth an estimated $1 billion this year.

Ashlee hopes her venture into fashion will be inspirational for young girls wanting to experiment with their personal style: "My goal as co-creative director will be to design clothes that will help inspire young girls to express their personalities and creativity through fashion."