By peoplestaff225
Updated June 02, 2008 10:56 AM

Calling his newlywed wife, Ashlee Simpson-Wentz, 23, his "baby mama," rocker Pete Wentz, 28, of the band Fall Out Boy, performed for the grand opening of Palms Place in Las Vegas on Saturday, May 31st. On hand were both his wife — who is pregnant with the couple’s first child and due in the fall — and his sister-in-law, singer Jessica Simpson, 27, who watched the concert from the audience.

As for Jessica, she has no doubt that her younger sister will make a great mom saying that "she will be an amazing mother" and calling them both an inspiration to her music.

During the event that night, Jessica and Ashlee stuck by each other’s side taking pictures for the media and spending their time in the VIP section of the club. Jessica, who is obviously excited to become an aunt, took quite a few pictures with her hand resting on Ashlee’s tummy.

Source: People; Photo by Denise Truscello/
| Credit: Denise Truscello/WireImage

Thanks to CBB readers Manda Jo and Mary Beth.