U.S. recording artist Ashlee Simpson is expecting her first child with fiance Pete Wentz, a source confirmed for Usmagazine.com. Simpson is the younger sister of singer and actress Jessica Simpson. Wentz is the frontman of the pop group Fall Out Boy. The pair announced their engagement last week. "We are thrilled to confirm their engagement and congratulate this happy couple," the couple's representative told Usmagazine.com. "Beyond that there is nothing to say."