Jessica Simpson talked about having babies this weekend. Well, her sister, Ashlee Simpson-Wentz, having babies, that is.

“I want her to have another baby,” Jessica said at Ash’s 25th birthday celebration on Saturday at the Wet Republic pool in Las Vegas. “I want another nephew or a niece.”

The Melrose Place star, along with her big sister, jetted into Sin City on Saturday morning with family and friends, including hubby Pete Wentz and parents Tina and Joe.

Holding court in a private bungalow, Ash was surprised with a three-tiered cake topped with cupcakes.

Not sure if this has anything to do with the not-dating-anyone Jessica, but…

Ashlee jumped on the mic and asked the DJ to play Beyoncé’s “Single Ladies.” She not only asked all bikini-clad women to do the signature dance, but Ashlee did her own to cheers and applause. She then joined the crowd for some more dancing.

I’m told the partying group was back in L.A. a few hours later after catching an early evening flight home.

The next night, Pete cleaned up his look during the Fall Out Boy concert at New York’s Madison Square Garden. At the end of the show, Wentz announced, “This is the death of the emo haircut,” followed by having his long locks buzzed off by bandmate Mark Hoppus.

Now, back to Las Vegas for a moment. Also in the gambling mecca for the weekend were Jessica’s ex-hubby, Nick Lachey, and his girlfriend Vanessa Minnillo, who took in the Friday night performance of The Beatles LOVE by Cirque du Soleil at the Mirage.

Ms. Minnillo was also spotted helping the Mirage celebrate its 20th anniversary at parties at the Bare Pool Lounge and Jet nightclub, as were Courtney Love, Nicole Scherzinger and Chris Daughtry, among others.

Kylie Minogue performed on Saturday at the Pearl at the Palms Casino Resort as part of her first North American tour. Taking seats in the VIP skyboxes were Paris Hilton and boyfriend Doug Reinhardt, who capped off the night at nightclub Body English.

- Source: eonline.com