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Happy Birthday, Jessica Simpson!

Jessica turns 31 on Sunday. The buxom blonde's had her fair share of heartbreak throughout the years, but her sister Ashlee, 26, has always stood by her side.

"People compare us all the time and all day long and we don't care," Ashlee told "We are like so not in comparison. We just love each other." 

PHOTOS: Jessica's biggest fashion obsession

Jessica rose to fame before her kid sister, but her support for Ashlee has been unwavering. "I'm her biggest fan," Simpson gushed.

In June 2011, the sisters announced they'd be creating a tween apparel collection together as part of the Jessica Simpson Collection. "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," Ashlee said. Jessica's fashion empire is already worth over $750 million.