Jessica Simpson Celebrates Nephew Bronx's Birthday With Sister Ashlee Simpson—See the Pics

Pete Wentz was also there as his son turned five

Talk about your family get-togethers!

Jessica Simpson stepped out to celebrate nephew Bronx's fifth birthday at The Coop in Studio City, Calif., on Saturday, Nov. 16.

But she definitely wasn't the only one.

The blond bombshell was joined by fiancé Eric Johnson and the couple's two kids, daughter Maxwell and newborn son Ace.

Additionally, Bronx's parents, Ashlee Simpson and Pete Wentz, were on hand.

But wait, there's more!

Ashlee and Pete also brought along their new significant others, Evan Ross and Meagan Camper, respectively.

And Jessica and Ashlee's dad Joe Simpson swung by as well to wish his grandson a happy birthday.

But the real star power undoubtedly came from one guest in particular—none other than Evan's mom, Diana Ross.

Earlier this month, Jessica flaunted her fabulous post-baby body in a photo she shared on Twitter.

"Couldn't stop smiling on set for my new @weightwatchers campaign today!" the 33-year-old captioned the pic.

It was recently announced that the fashion mogul was making a return to Weight Watchers following the birth of Ace back in June.