Jessica Simpson's daughter Maxwell is reaping the benefits of being born to a mom who's estimated to be worth a billion dollars ... and she's only a month old!

"She is definitely spoiled," said Jessica's sister Ashlee Simpson to Us Weekly. "You should see her closet! I'm like, 'God I wish I had your closet!' Her closet is beautiful." And we wish we had your closet, Ash. Or maybe Jessica's. Yeah, definitely Jessica's -- especially she's expanding her own clothing line to include maternity wear!

Jessica has been spending the first month of motherhood at home bonding with baby Maxwell, and Ashlee, who's mom to three-year-old son Bronx, is beaming with pride.

"I am so proud of her," the new aunt said. "There were small things here and there [I advised her on] that you ask your friends and other mothers [about], but other than that, she's great." For her part, Jess is enamored with her little girl. “We stare at her all the time,” she said about fiancee Eric Johnson and her little girl. “We can’t get enough.”

We admit it. These two are our favorite pair of sisters in the business. Aside from Mary-Kate and Ashley Olsen, of course.