Ashlee Simpson: My Son Bronx, 4, Is "Protective" of Jessica Simpson's Daughter Maxwell, 9 Months

USMagazine, Friday, February 1, 2013, 8:30am (PST)

Ashlee Simpson is a proud mom, aunt and honorary aunt-to-be! The single mother-of-one chatted with Us Weekly at Svedka Vodka's Valentine's Day Throwback Thursday Bash on Jan. 31 in West Hollywood about her growing son Bronx, 4, sister Jessica Simpson's second pregnancy and pal Cacee Cobb's own baby news.

"He is definitely the sweetest kid. He is brilliant," the 28-year-old mom, who shares custody of Bronx with ex-husband Pete Wentz, gushed to Us. "He's got his own ideas, his own way of thinking. He is a jokester. He hides. He definitely will sneak around, play hide and seek. He'll get you and any joke. He's always very creative and he is pulling pranks on us all the time."

PHOTOS: Ashlee and Pete in happier times

Bronx loves superheroes -- and, like his mom and dad, digs music!

In addition to loving super heroes, Ashlee says her son is into music just like his parents.

"He does like music but he's picky. He'll tell you if he likes a song or doesn't," she explained. But his strong opinion is actually very helpful to his singer mom. "That way I know too," she said. "If I write a song and he doesn't like it I won't do it."

PHOTOS: The Simpson sisters through the years

Bronx is also a very devoted cousin to Jessica's 9-month-old daughter, Maxwell. "He is definitely protective, and he's so excited about every time she's growing," Ashlee told Us. "He loves that stuff!"

And, with Aunt Jessica's surprise second pregnancy, he'll have a second little cousin to meet later this year. 

Has Ashlee been giving pregnant-again Jessica any parenting advice? "Oh, I don't have to," she said. "She's on her second!"

PHOTOS: Adorable A-list couples

There's even more babies on the way in the extended Simpson family's inner circle: Cobb, Jessica's former personal assistant and close friend, announced her own pregnancy on Thursday (Jan. 31). 

And Ashlee says she has plenty of well wishes to give Cobb and husband Donald Faison. "Are you kidding? That's my other sister!" she exclaimed. "So of course!"

This article originally appeared on Usmagazine.com: Ashlee Simpson: My Son Bronx, 4, Is "Protective" of Jessica Simpson's Daughter Maxwell, 9 Months